Effect of microbial inoculant or molasses on fermentative quality and aerobic stability of sawdust-based spent mushroom substrate

Significance Statement

Rise in feed costs will lead to rise in the production costs of animal based food in future. Hence in future, there will be a new demand for inexpensive feed from underutilized resources. Mushroom growing is a gradually developing eco-friendly activity which generates tonnes of Spent Mushroom Substrate (SMS), a year. SMS are the remains of Mushroom harvest.

In some parts of the world, this residual material is underutilized. This leads to environmental problems such as landfill accumulation and can be a greater nuisance. Hence it is necessary to effectively recycle the residual material. SMS decays rapidly as it has high moisture content and hence it needs to be processed quickly.

Professor Kwak and colleagues from South Korea came up with an effective technique which uses lactic acid in fermentation process. This lactic acid fermentation technique is simple and the process is done under anaerobic condition. In this technique, clostridia growth and other microbial population are suppressed. Lactic acid is efficiently produced by eco-friendly lactic acid bacterial inoculants. These inoculants are safe and non-corrosive to machinery equipment. The ensiling characteristics are determined greatly by the compatibility of the inoculants between its strain and plant biomass.

Many lactic acid bacterial strains are isolated from the ensiled SMS of which Lactobacillus plantarum is identified as the most efficient acidifiers at lactate production. The quality of fermentation of cotton waste-based SMS silage is improved by combining Lactobacillus plantarum with molasses and yeast but there were no reports on saw dust-based SMS. Hence two experiments were performed; one with an objective of selecting the strain with silage quality parameters and other with an objective to study silage conservation characteristics and how it is affected.

The research team took samples of fresh SMS from the biomass and the inoculants suspended in deionized water are sprayed on the material. The inoculants are uniformly applied with constant mixing. A hydraulic press is used to pack the treated SMS into polyvinylchloride silos. The silos are a kept at room temperature for about ten days. After ten days the silos are opened and the contents in it were mixed thoroughly and the samples were taken for chemical and biological analysis.

Compared with those before ensiling, 100% SMS (control) after ensiling showed unstable fermentative properties with high pH (5.2) and little lactic acid production. Compared with the ensiled control, treatments (T1, T2 and T3) resulted in decreased pH, 18–20 times higher concentrations of lactic acid, and greater populations of total bacteria, LAB and yeast . The addition of 5% molasses, 0.5% LAB and 0.5% yeast (T3) to the SMS resulted in the lowest pH (4.25) and the greatest microbial populations. Treatment T3 was selected for a large scale silo study which was ensiled for 10, 20 and 30 d. As in the small-silo study, the T3 treatment showed favorable fermentative and microbial parameters, compared with the control, by decreasing pH and increasing lactic acid concentrations, LAB and yeast populations. The minimum ensiling period was 20 d, when pH was reasonably low and LAB and yeast populations were greatest.

In order to determine the aerobic deterioration, the samples are subjected to aerobic stability test. The extent of aerobic stability varied depending on the ensiling environment. The aerobic stability of the Lactobacillus treated SMS after 28 days of ensiling lasted for 84 hours. They also found that the packing density and the exclusion of oxygen will have an impact on the extent of aerobic stability. Thus, this study identified Lactobacillus plantarum as the best strain for SMS fermentation. In conclusion, molasses and microbial inoculation improved silage quality of SMS.  

 

About the author

Wan Sup Kwak

Full Professor at Division of Food Bio-science, Konkuk University in Korea.

Received Master and PhD degrees at Virginia Tech, USA in 1990.

Won 2004 yr research award from Journal of Animal Science & Technology, Korea.

Served as a editor-in-chief of Journal of Korean Livestock Facility & Environment.

Presently serve as an editorial board of an international Journal of Research of Animal & Veterinary Science in Pakistan.

Specialize in not only co-product recycling as animal feed of poultry litter, garlic stalk, spent mushroom substrate and other organic waste but also effective use of co-products as ingredient of total mixed ration (TMR) for functional, high quality of beef production.

and start from 2017 a 3 yr-governmental research project in use of fruit and vegetable by-product as feed.  

Journal Reference 

Kim JS1, Lee YH1, Kim YI2, Ahmadi F1, Oh YK3, Park JM2, Kwak WS4Effect of microbial inoculant or molasses on fermentative quality and aerobic stability of sawdust-based spent mushroom substrate, Bioresource Technology, Volume 216, 2016, Pages 188-195.
Show Affiliations
  1. Division of Food Bio-science, College of Medical Life Sciences, Konkuk University, Chungju, Chung-Buk, Republic of Korea.
  2. Egreen Co. LTD, Icheon, Gyeong-Gi, Republic of Korea.
  3. National Institute of Animal Science, RDA, Jeonju, Jeon-Buk, Republic of Korea.
  4. Division of Food Bio-science, College of Medical Life Sciences, Konkuk University, Chungju, Chung-Buk, Republic of Korea. Electronic address: [email protected]

 

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