Cultivation of gourmet mushrooms using brewer's spent grain

Final Report for FNE14-795

Project Type: Farmer
Funds awarded in 2014: $14,997.00
Projected End Date: 12/31/2015
Region: Northeast
State: Massachusetts
Project Leader:
Mycoterra Farm
Mycoterra Farm
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Project Information

Summary:

Brewers’ spent grain (BSG) was tested as a substitute for standard spawn material and fruiting substrate supplements in the production of Pleurotus ostreatus (Oyster), Lentinula edodes (Shiitake) and Hericium erinaceus (Lion’s Mane) mushrooms at Mycoterra Farm in Westhampton, MA. BSG is a waste product of commercial breweries; it is produced in large quantities, and has been previously identified as potential alternative nutrient source in mushroom cultivation.  For Shiitake and Lion’s Mane, the wood lovers, mushroom production involves a vegetative scale-up process where the mycelium progresses from petri dish to first-generation grain spawn to second-generation grain spawn to sawdust spawn to fruiting substrate consisting of sawdust and grain supplements.

BSG was substituted for rye berries in the first and second-generation stages of spawn production for all species. For Oyster mushrooms, this vegetative scale-up of spawn was attempted three times, however each trial resulted in failure in the treatment batches and the study was unable to observe the final fruiting stages for the Oyster mushroom. For Shiitake and Lion’s Mane, the sawdust spawn generated in the third stage of the experiment was used to inoculate final fruiting substrates. Consistent and significant differences in the data for each scale-up stage of Part A indicated BSG is unsuitable as a spawn material. The grain was much wetter than anticipated. While it is easy to adjust a dry substrate to a higher moisture content, it is much more difficult reducing moisture content.

While significantly different from controls in terms of contamination rates and colonization times, the spawn from the vegetative scale-up process did successfully produce fruiting units in the final stage. BSG was used as a substitute for wheat bran in this supplemented sawdust mix for fruiting Shiitake and Lion’s Mane mushrooms with mixed results. Lion’s Mane trials were inconsistent, but aggregate data indicated increased yields in the treatments. Shiitake production appeared to be inhibited by the substitutions of BSG both in the spawn stages and final fruiting stage.

At this scale it appears that the grain savings did not make enough of a difference to warrant BSG substitution solely for financial savings.

Based on the experience in this study we would recommend mushroom farmers interested in BSG substitution to avoid utilizing this by-product in the spawn stages and to focus future efforts on further exploration on use of BSG as a substitute in sawdust supplementation.

Results were summarized in posters for display in the Plant and Soil Sciences department at UMASS; PDFs of the poster were shared digitally within a network of mushroom farmers and the SARE network on Facebook.

Introduction:

Mycoterra Farm is a specialty mushroom farm in Westhampton, MA. The farm produces mushrooms year-round. Sterile laboratory techniques are used to facilitate vegetative propagation of the living tissue of the fungal organisms, called mycelium. The material is incubated in a controlled environment and fruited in greenhouse-like conditions. The bulk substrates required for mushroom production include locally sourced straw and sawdust, by-products of local agriculture and forestry industries. These materials are low cost and readily available. In addition to these materials, grains are required for spawn and supplementation in the mushroom production process. These grains are not locally produced in any significantly available quantities and represent a considerable cost for the farm. The project tested the effects of BSG as a substitute for rye grain in the vegetative scale-up and wheat bran in the fruiting steps of three mushroom species including Oyster, Shiitake, and Lion’s Mane. Rye berries are used for the standard spawn substrate at Mycoterra Farm and the standard nitrogen supplement is wheat bran; both are organically certified products sourced through local distributors from Midwest farms. BSG is a waste product of commercial breweries; it is produced in large quantities, and has been previously identified as potential alternative nutrient source in mushroom cultivation.  Spent grain for the project was sourced from Berkshire Brewing Company (BBC) located in South Deerfield, MA. Julia Coffey, owner of Mycoterra Farm and Dylan Kessler were primary investigators. Chris Haskell assisted in production and maintenance. Nicholas Brazee assisted with statistical analysis.

Project Objectives:

The objective was to characterize feasibility of substituting brewer’s spent grain (BSG) for rye and wheat bran in the cultivation of three popular edible mushroom species: Oyster (Pleurotus ostreatus), Shiitake (Lentinula edodes) and Lion’s Mane (Hericium erinaceus). BSG is attractive as a grain substitute as it is a low cost and a locally available brewery industry by-product, yet few studies existed testing both the use of BSG as a spawn material and supplement for fruiting substrate. The effects of BSG substitution were measured through observation of contamination rate, colonization time, total yield and biological efficiency.   Ultimately, the goal in investigating BSG utility in mushroom production is to reduce the costs of farm inputs; financial impacts were also examined.  

Cooperators

Click linked name(s) to expand
  • Dr. Nicholas Brazee
  • Chris Haskell
  • Dylan Kessler

Research

Materials and methods:

The project was divided into four parts. Part A included three subgroups (A1-A3) testing the effects of BSG as a substitute for rye grain in each of the vegetative scale-up steps of spawn. Part B tested the effects of the substitution of BSG for rye grain in the spawn stages in the subsequent fruiting step of Shiitake and Lion’s Mane. Part B was tested alongside Part C1 and C2, which involved replacement for bran as a nitrogen source in the fruiting step of Shiitake and Lion’s Mane. The project was cumulative; each of the B, C and D treatment groups relied on success in the spawn generation stages of A1-A3. As such, substitution for rye grain in the fruiting step of Oyster mushrooms, Part D, was never achieved due to failures in the A1 and A2 stage. Our methods for materials preparation, sterilization, incubation, fruiting and data collection are described in detail below.

See:    Figure.1.Experimental.Design.jpg


Background Preparation

Petri dishes of each species were prepared between 2-3 weeks prior to each A1 group inoculation. Agar media was sterilized at 17-20psi for 45 minutes. The sterilized agar media was poured into pre-sterilized plastic petri dishes. The dishes were cooled and allowed to set overnight. Each dish was inoculated with a 1cm square wedge of mycelium, closed and wrapped in parafilm to incubate until ready for use.

Part A) BSG substitute for rye berries in the vegetative scale-up steps of spawn production.

Part A included three sub-groups: A1- first generation grain spawn; A2 – second generation grain spawn; and A3 -sawdust spawn. Steps A1 and A2 were performed with all species. A1 control and treatment spawn were used for inoculation of A2. Lion’s Mane and Shiitake were replicated two times. Oysters were replicated three times. A3 was performed with Shiitake and Lion’s Mane; each species was replicated two times. In A3, control and treatment spawn from A2 was transferred to sawdust bags, which were subsequently used as spawn for the final fruiting stages.

Sub-Group A1) Substitution of BSG for Rye Berries in First Generation Grain Spawn

For each species, the first round of A1 first-generation grain spawn consisted of 18 control jars and 18 treatment jars. The control jars contained 200g rye grain, 200g water, and 2g gypsum. The treatment jars contained identical mass of BSG, 400g and 2g gypsum. The jars were sterilized simultaneously at 17-20 psi for 60 minutes. Both groups were inoculated with 2 square centimeters of agar culture. One petri dish was used to inoculate 3 control jars containing rye berries and 3 treatment jars containing BSG. The jars were shaken and shelved in the lab for incubation.

The second round of A1 spawn consisted of 36 control and 36 treatment jars for both Oyster and Lion’s Mane and 30 control and 30 treatment jars for Shiitake. The formulas were repeated as above with greater effort made in reducing moisture content of the BSG.   A third round of A1 jars were prepared for Oyster as follows: 17 treatment jars containing: 400g BSG and 2g gypsum; 21 control jars containing: 200g rye grain, 200g water, and 2g gypsum; and a mixed treatment consisting of 16 jars containing 100g rye grain and 300g BSG and 2g gypsum. Growth was monitored daily and judged on a scale from 0 – 5 until full colonization in each jar was achieved. Frequency of contamination within groups was noted.

Sub-Group A2) Substitution of BSG for Rye Berries in Second Generation Grain Spawn

A2 involved two treatments and a control. The first treatment (A2.1) involved scaling up first generation grain spawn controls from A1 to spawn bags containing 2400g sterilized BSG and 6g gypsum to create second-generation grain spawn. The second treatment (A2.2) involved scaling up first-generation grain spawn derived from the A1 treatment group onto 2400g sterilized BSG and 6g gypsum. The control (A2.3) simply scaled up first-generation grain spawn from A1 control group onto 1400g rye berries prepared with 1000ml water and 6g gypsum.

The first two rounds of Oyster each included 9 replicas for A2.1, 11 replicas for A2.2 and 9 replicas of A2.3.   The third round of Oyster replicas were increased to 14 replicas for A2.1, 12 replicas for A2.2 and 17 replicas of A2.3. The first A2 round of Lion’s Mane had 8 replicas for A2.1, 11 replicas for A2.2 and 8 replicas of A2.3. The second round of Lion’s Mane had 16 replicas for A2.1, 16 replicas for A2.2 and 16 replicas of A2.3. The first round of Shiitake had 8 replicas for A2.1, 8 replicas for A2.2 and 9 replicas of A2.3. The second round of Shiitake had 15 replicas for A2.1, 15 replicas for A2.2 and 13 replicas of A2.3. Each A2 batch was allowed to incubate 2-4 weeks until full colonization was achieved. Data was measured as in A1.

Sub-Group A3) Substitution of BSG Grain Spawn in Sawdust Spawn

The control and treatment in Sub-Group A3 each consisted of 40 sawdust bags. The control was inoculated with A2 rye at a rate of 1:6. The treatment replaced rye inoculum with the most successful A2 treatment. Moisture contents ranged 65-70%. Data was measured as in A1, however colonization in individual blocks was not tracked. Each A3 batch was allowed to incubate until fully colonized; these “sawdust spawn” blocks were retained for multiple rounds of inoculation over a several week span.  A3 was done in duplicate for both Shiitake and Lion’s Mane.   A3 spawn was used in B and C.

Part B) Substitution for rye grain in fruiting step of Shiitake and Lion’s Mane.

Part B tested the effects of replacing rye berry inoculum with BSG on the Biological Efficiency (BE) in the fruiting stages of Shiitake and Lion’s Mane grown on the standard supplemented sawdust mix. The treatment replaced the inoculum with A3 treatment; the control used A3 control sawdust spawn.

Part C) A replacement of BSG for bran as a nitrogen source in the fruiting step of Shiitake and Lion’s Mane.

Part C tested the effect of BSG as a bran replacement on BE in Shiitake and Lion’s Mane. There were two C group treatments: Sub-Group C1 – Control spawn onto BSG supplemented sawdust; and Sub-Group C2 – BSG spawn onto BSG supplemented sawdust.

In order to be able to compare between the B, C1 and C2 treatments they were prepared simultaneously alongside a control group. The four groups were prepared from two different supplemented sawdust batches. The first batch of standard supplemented sawdust mix consisted of eight buckets hardwood sawdust, two 20kg bags wheat bran and one-quart gypsum. Twenty 5-pound bags prepared for both the control group and the B treatment. The second batch used three 5-gallon buckets of BSG instead of wheat bran. This was used for the C1 and C2 sample groups; twenty 5-pound bags were prepared from the alternative sawdust mix for each of these two groups. Moisture content was adjusted to 65-75% for both the control and treatment groups. All media was autoclave sterilized at 17-20 psi for three hours prior to inoculation.

The A3 treatment and control spawn were used for multiple replicas in parts B, C1 and C2. Controls and treatments were incubated in identical environments. B and C groups were performed with Shiitake and Lion’s Mane. Shiitake was replicated five times and Lion’s Mane was repeated four times where fruiting data was collected successfully for both species. Other attempts resulted in failure in some of the treatment groups prior to the fruiting stage and fruiting data were not recorded. Bags were observed daily until full colonization, noting growth rate, colonization time, and contamination rate. Once all treatments achieved full colonization, fruiting was then initiated in the grow room. The first fruiting flush of each batch was harvested over a two-week period and weighed fresh and dried.

Data Collection

Colonization times, contamination rates and yields were all tracked. Colonization progress was tracked using a semi-quantitative 0 (uncolonized)-5 (fully colonized) scale. Completion of colonization on a per bag/jar basis was tracked in A1 and A2. ANOVA was performed for individual colonization times in A1 and A2 in order to determine effect of BSG on colonization times. Fisher’s least significant difference was used to determine significance. Time to complete batch colonization for parts A3, B, C and D was noted, but not tracked on an individual basis and therefore stats were not performed. Contamination in parts A1-A3 indicated failure of the jar/bag. Contamination in B, C or D was noted, and contamination beyond a low threshold before the first flush completes indicated failure in some treatments. During the colonization period of each step, photographs were used for documentation of notable colonization and contamination data.  

The aggregate weight of the first flush was weighed fresh to determine yield of each treatment. Wet weight is effective measure of “financial efficiency” in the marketplace since mushrooms will be sold fresh. The market worth of the mushrooms produced in each treatment will be determined by multiplying batch weight by standard retail price per pound. The cost of rye and wheat bran was subtracted from gross income to determine the financial efficiency.

In the mushroom industry, Biological Efficiency (BE) is the standard measure of mushroom yield vs. energy input, and is considered essential to evaluating the success of fruiting parameters. The formula is: BE % = (fresh weight of mushrooms / dry weight of substrate) * 100 (Chang et al. 1981). After fresh weights were measured, aggregate dry weights were also measured in order to account for any major differences in water content between treatments.

See:    Chart.1.SARE.A1 anova.xlsx

            Chart.2.SARE.A2 anova.xlsx

            Chart.3.SARE.A3.xlsx

            Chart.4.SARE.B.C.xlsx

 

Research results and discussion:

Part A: In all three subgroups the BSG substitution was correlated with longer colonization times and higher contamination rates. This was consistent between all three species.   BSG correlated with lowered colonization levels, and in certain cases inhibited complete colonization, likely due to high moisture content.

Subgroup A1)

All Subgroup A1 trials indicated the BSG sample jars were significantly different from the controls. High moisture content of the BSG was likely the major factor influencing colonization rate and extent. However, qualitative observations led to the conclusion that even BSG adjusted to ideal moisture content would be a less-than-ideal spawn material due to the nature of the processed grains, especially in the A1 stage.

The BSG spawn jars ANOVAs were performed for the date on which one set of jars (usually control) colonized fully, or barring this, the final measurement date.  

Summary of ANOVAs for A1:

  • Pleurotus ostreatus A1-1 – Analysis done for April 30, when all control jars were fully colonized. Sample jars colonized fully by May 1, the final measurement day. 1/18 (5.5%) sample jars contaminated. 0 control jars contaminated. P=0.00518, based on colonization time, sample and control were significantly different.
  • Pleurotus ostreatus A1-2 – Analysis done for June 9, when all control jars were fully colonized. 14/36 (38.8%) sample jars contaminated. 8/36 (22.2%) control jars contaminated. P=0.0009, based on colonization time, sample and control were significantly different.
  • Pleurotus ostreatus A1-3 – Analysis done for November 6, day when all mixed sample jars were fully colonized. All control jars and pure sample jars colonized fully by 11/8, the final measurement day. 3/17 (17.6%) pure sample jars contaminated. 2/15 (13.3%) mixed sample jars contaminated. 0/21 control jars contaminated. P=0.00009. Results of Fisher’s LSD test indicate sample groups significantly different from control, but not each other.
  • Hericium erinaceus A1-1 – Analysis done for May 5, when all control jars were fully colonized. 2/18 (11.1%) sample jars contaminated. 2/18 (11.1%) control jars contaminated. P=0.00253, based on colonization time, sample and control were significantly different.
  • Hericium erinaceus A1-2 – Analysis done for July 1, when all control jars were fully colonized. Sample jars colonized fully by May 9, the final measurement day. 2/18 (11.1%) sample jars contaminated. 2/18 (11.1%) control jars contaminated. P=0 , based on colonization time, sample and control were significantly different.
  • Lentinula edodes A1-1 – Analysis done for 5/24, when all control jars were fully colonized. 1/18 (5.5%) sample jars contaminated. 0 control jars contaminated. P=3.00E-13, based on colonization time, sample and control were significantly different.
  • Lentinula edodes A1-2 – Analysis done for July 14, final measurement date. 3/30 (10%) sample jars contaminated. 1/30 (3.3%) control jars contaminated. P=7.66E-8 based on colonization time, sample and control were significantly different.

See:    Figure.2.A1.Colonization.Contamination.jpg

Summary of Colonization and Contamination for A2:

  • Pleurotus ostreatus A2-1 – No analysis done due to high contamination levels. Control fully colonized by May 15. 2/9 (22.2%) control bags contaminated, 8/9 (88.8%) BSG to BSG contaminated, 5/6 (83.3%) Rye to BSG contaminated
  • Pleurotus ostreatus A2-2 – No analysis done due to high contamination levels. Control fully colonized by June 18. 0/9 control bags contaminated, 10/11 (90%) BSG to BSG contaminated, 9/9 Rye to BSG contaminated
  • Hericium erinaceus A2-1 – Analysis done for May 23, when all control bags were fully colonized. 1/8 (12.5%) control bags contaminated. 1/8 (12.5%) BSG to Rye sample bags contaminated. 4/11 (36.4%) BSG to BSG sample bags contaminated. P=0.134 samples and control not significantly different.
  • Hericium erinaceus A2-2 – Analysis done for July 14, the final measurement day, when all control bags were fully colonized except one which was at 4. 0 control bags contaminated. 2/16 (12.5%) BSG to Rye sample bags contaminated. 0/11 BSG to BSG sample bags contaminated. P=6.80E-4. Results of Fisher’s LSD test indicate sample groups significantly different from control, but not each other.
  • Lentinula edodes A2-1 – Analysis done for June 12, when all control bags were fully colonized. 0 bags were contaminated. P=1.43E-5. Results of Fisher’s LSD test indicate all groups significantly different from each other.
  • Lentinula edodes A2-2 – Analysis done for August 6, when all control bags were fully colonized. 0 bags were contaminated. P=0.263 samples and control not significantly different.

See:    Figure.3.A2.Colonization.Contamination.jpg

 

Summary of Colonization and Contamination for A3:

BSG increased contamination rates and decreased spawn viability somewhat for both Shiitake and Lion’s Mane. The A3 BSG sample bags consistently took longer (2-4 days) to fully colonize and exhibited higher contamination rates (12.5-15% vs. 2.5-5%) than control material.

 

  • Hericium erinaceus A3-1 – The sample took 24 days to fully colonize. 5/40 (12.5%) of sample bags were contaminated. The control took 20 days to fully colonize. 2/40 (5%) of control bags were contaminated.

 

  • Hericium erinaceus A3-2 – The sample took 22 days to fully colonize. 6/40 (15%) of sample bags were contaminated. The control took 20 days to fully colonize. 1/40 (2.5%) of control bags were contaminated.

 

  • Lentinula edodes A3-1 – The sample took 20 days to fully colonize. 5/40 (12.5%) of sample bags were contaminated. The control took 16 days to fully colonize. 1/40 (2.5%) of control bags were contaminated.

 

  • Lentinula edodes A3-2 – The sample took 20 days to fully colonize. 5/40 (12.5%) of sample bags were contaminated. The control took 16 days to fully colonize. 1/40 (2.5%) of control bags were contaminated.

 

See:    Figure.4.A3.Colonization.Contamination.jpg

Parts B, C1 and C2)

In Parts B and C yields were expressed using total first flush weight and wet and dry Biological Efficiency, a measure of conversion of raw substrate to mushrooms.

Hericium erinaceus It is unclear how BSG affected Lion’s Mane yields within four replicates of parts B, C1 and C2. The data from trial to trial was irregular. The aggregate data shows minor differences between treatments. Ultimately, BSG doesn’t appear to have decreased Lion’s Mane yields in this study, and could potentially be used as a wheat bran substitute without adversely affecting yields. Further study is warranted. Biological Efficiency data is exhibited for each of four trials in figures 5-8. Aggregate Biological Efficiency data is displayed in figure 9.

See:    Figure.5.HE.BE.Trial1.jpg

            Figure.6.HE.BE.Trial2.jpg

            Figure.7.HE.BE.Trial3.jpg

            Figure.8.HE.BE.Trial4.jpg

            Figure.9.HE.BE.All.jpg

Lentinula edodes – BSG likely caused significantly decreased Shiitake yields. Use of BSG in spawn correlated with decreased Shiitake yields. Use of BSG as a nitrogen source correlated with further decreased Shiitake yields. Biological Efficiency data is exhibited for each of five trials in figures 10-14. Aggregate Biological Efficiency data is displayed in figure 15.

See:    Figure.10.LE.BE.Trial1.jpg

            Figure.11.LE.BE.Trial2.jpg

            Figure.12.LE.BE.Trial3.jpg

            Figure.13.LE.BE.Trial4.jpg

            Figure.14.LE.BE.Trial5.jpg

            Figure.15.LE.BE.All.jpg

Part D) Substitution for rye grain in fruiting step of Oyster mushrooms.

BSG was unsuitable for Oyster cultivation due to high moisture content that led to contamination. Trial D was never achieved due to failures in the A2 stage.  For Oyster mushrooms the A1 and A2 stages were completed three times. Due to contamination that pervaded in the A2 stages, the Oyster mushroom trials never made it to the D stage, where BSG was to substitute for the rye inoculum on pasteurized straw substrates. During the subsequent batches of A1 and A2, adjustments were made in attempts to find a viable formula including reducing moisture content and mixing spent grain with rye. Despite our best efforts, it was determined that spent grain failed as a viable substitute for Oyster mushrooms in our process at Mycoterra Farm. Observation of the Oyster mushroom on the BSG substrate indicated excessive moisture seemed to be the major impediment to the success of this species in colonizing the spent grain.

Additional Impacts

Mushroom farming using sterile laboratory technique has an inherent ripple effect whenever a new technique or material is introduced into the production environment. The primary impacts were observed in the form of new contaminants found in both the lab and incubation environment. These included mold, bacteria and yeast organisms. Contaminants were not identified to species but were isolated and removed upon discovery. The primary contaminants usually observed at Mycoterra Farm prior to the project are Trichoderma spp, (green mold). During the study contamination was first observed in A1 and A2 stages, however as the study drew on, cross contamination occurred with other farm stock. As only the BSG treatments exhibited contaminants at first, it is assumed the origin of the contaminants.   Given the microbial nature of brewing itself, it is not surprising that new contaminants correlated with the introduction of BSG into the mushroom farm environment.

Financial Efficiency

The financial efficiency essentially followed the same trends as yield data. Harvest weights were multiplied by the retail price per pound that Mycoterra Farm sells mushrooms for at market: $15/lb. The cost for rye and wheat bran was subtracted from the appropriate treatment. Rye berries for the Control and C1 treatments cost $4.00 each. Wheat bran for the Control and B treatments cost $6.00 each. Therefore the grain costs per treatment were as follows: Control: $10; B: $6.00; C1: $4.00; and C2: $0.00. The adjusted gross reflects the total gross adjusted for grain savings. At this scale it appears that the grain savings did not make enough of a difference to warrant BSG substitution solely for financial savings. The additional time required for inoculation of the treatment groups in the A1 and A2 stages was not documented and could not be factored into the financial efficiency of BSG substitution in the spawn stages of the B and C2 groups. This could add considerably to the labor costs. In the C1 and C2 treatments, labor costs were not impacted, as the BSG substitution required no additional time. At this scale financial incentives of substituting BSG are negligible. However, larger production batches would incur more significant savings worthy of considering BSG as a fruiting supplement.

See:    Chart.5.LionsMane.Financial.Data.pdf

            Chart.6.Shiitake.Financial.Data.pdf

Research conclusions:

The study was most successful in ruling out BSG substitution for rye berries in the spawn stages of mushroom production.   Consistent and significant differences in the data for each scale-up stage of Part A indicated BSG is unsuitable as a spawn material. The grain was much wetter than anticipated. While it is easy to adjust a dry substrate to a higher moisture content, it is much more difficult reducing moisture content. The high moisture content of the BSG was a major factor inhibiting colonization and contributing to contamination. Mycelium has a limited ability to tolerate anaerobic environment. Each species has different thresholds for growing in semi-saturated substrates. Obtaining low enough moisture content for a tolerable threshold was particularly challenging for our Oyster strain; Shiitake and Lion’s Mane were both more successful. The saturated conditions also created favorable environments for anaerobic organisms and other contaminants; new contaminants were observed for the first time in the lab during the study.  

The nature of the BSG spawn made it quite difficult to work with, particularly in the A1 and A2 spawn stages. Both the excessive wetness and the mashed nature of the grain made for a clumpy mess. In the A1 stage the wetness of the BSG proved most physically troublesome. Sticky, wet material made filling the jars difficult. Following inoculation with the agar wedges, it was difficult to distribute the inoculum, and the grain left residue on the jar and filter-patch fitted lids. Such residues are potential sites for contamination to develop, as evidenced in the course of the study: contamination in the BSG jars often began on the grain that adhered to the filter patches. The clumpy nature of the BSG was most cumbersome during the A1 to A2 inoculations. It is critically important these inoculations proceed smoothly and swiftly, with minimal movements and contact. Typically rye grain is loosened by shaking and poured into the open sterilized grain bag with a quick turn of the jar. The clumpy nature of the SBG made swift transfer challenging, often requiring forcible shaking or slamming of the jar over the open bag.   Such excess movement can spread contaminants, causing failure in subsequent growth stages. It also added considerable time to the A1 to A2 inoculation process itself.  

The study was successful in identifying potential formulas for replacing wheat bran in the fruiting stage of the Lion’s Mane mushroom. The data indicated Shiitake did not respond favorably. However, with adjustments to the supplementation ratio, comparable yields could potentially be achieved when substituting BSG for wheat bran.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

Two large posters summarizing the findings of this study were printed for display in the plant and soil sciences department at University of Massachusetts Amherst and display at special events, including but not limited to NOFA conferences. A pdf graphic of this poster was shared via email with several mushroom farmers in Mycoterra Farm’s professional network. This pdf was also shared within the Commercial Mushroom Growers Network Facebook group and within the SARE Facebook network. This report will also be shared with the above audiences.

Project Outcomes

Assessment of Project Approach and Areas of Further Study:

Future Recommendations

Based on the experience in this study we would recommend mushroom farmers interested in BSG substitution to avoid utilizing this by-product in the spawn stages and to focus future efforts on further exploration on use of BSG as a substitute in sawdust supplementation. Extreme care is suggested in handling the material to avoid cross-contamination of the laboratory environment. As the biological load of BSG dramatically increases with time after grain is pressed in the brewery environment, it is suggested to source BSG directly at the time of batch preparation; unused material should be discarded at a location remote to the laboratory. Personnel responsible for mixing and bagging bulk substrates should avoid entering the laboratory after working with BSG unless showered and furnished with a complete change of clothes and footwear.   Care should be taken to ensure complete sterilization is achieved to avoid introducing contaminants into the inoculation lab. Frequent observation of incubating units is further suggested; immediate isolation and removal of contaminate material is necessary to avoid cross-contamination.

Substitution of BSG for wheat bran as a nitrogen supplement was most successful for the Lion’s Mane mushroom, indicating potentially higher harvest weights are possible. Further study of BSG as a substitute in Lion’s Mane production with larger batch sizes is recommended to further explore this potential. While the study showed a decrease in Shiitake yields when substituting BSG for wheat bran, further experimenting with supplementation levels is suggested. Shiitake are particularly sensitive to substrate nitrogen levels. Excessive nitrogen can inhibit first-flush fruiting as much, and sometimes more so, than insufficient supplementation (Stamets, 1993). It is likely this study missed the target nitrogen with the BSG supplementation rate used. Further experimentation with different BSG supplementation rates is recommended for Shiitake.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.