Lignocellulose utilization and bacterial communities of millet straw based mushroom (Agaricus bisporus) production

Abstract

Agaricus bisporus is in general cultivated on wheat and rice straw in China. However, millet straw is a potential alternative resource for Agaricus bisporus cultivation, but this has hardly been studied. In the present study, the feasibility of millet straw based mushroom production was analyzed by three successive trials. Mature compost demonstrated high quality with total nitrogen, pH, and C/N ratio of 2.0%, 7.5, and 18:1 respectively, which was suitable for mushroom mycelia growth. During composting, 47–50% of cellulose, 63–65% of hemicellulose, and 8–17% lignin were degraded, while 22–27% of cellulose, 14–16% of hemicellulose, and 15–21% of lignin were consumed by A. bisporus mycelia during cultivation. The highest FPUase and CMCase were observed during mushroom flushes. Endo-xylanase had the key role in hemicellulose degradation with high enzyme activity during cultivation stages. Laccase participated in lignin degradation with the highest enzyme activity in Pinning stage followed by a sharp decline at the first flush. Yield was up to 20 kg/m2, as this is similar to growth on wheat straw, this shows that millet straw is an effective resource for mushroom cultivation. Actinobacteria, Bacteroidetes, Chloroflexi, Deinococcus-Thermus, Firmicutes, and Proteobacteria were the dominant phyla, based on 16S rRNA gene sequencing during composting. The key environmental factors dominating bacterial communities of the samples were determined to be pH value, cellulose content, and hemicellulose content for prewetting and premixed phase of basic mixture (P0); moisture content for phase I (PI); and nitrogen content, lignin content, and ash content for phase II (PII), respectively.

Bacterial community diversity, lignocellulose components, and histological changes in composting using agricultural straws forAgaricus bisporusproduction

“…Our previous study ( Cao et al, 2018 ) showed that Thermobispora , Thermopolyspora , Ruminiclostridium , Thermobacillus, and Bacillus were the predominant genera bacteria in Phase I.T and II in wheat straw consistent with the present study. Studies by both Székely et al (2009) and Zhang et al (2019) supported our data as they found that the genera Thermopolyspora , Pseudoxanthomonas, and Thermobifida were more abundance in mature compost. In addition, it has been reported that the genus Thermopolyspora, comprising a cellulolytic actinomycetes species, is highly enriched in mature mushroom compost based on wheat straw ( Zhang et al, 2014 ).…”

“…The production of edible fungi has emerged as a potential biological use of agricultural AS, supported by low energy consumption and environmentally impact. Given the large variety of agricultural waste likely to be generated across China, the focus is mainly on the most prominent residues, such as rice straw, wheat straw, rye straw, and banana plant waste ( Zhang et al, 2019 ). Typically, AS are treated as lignocellulosic agricultural byproducts, which comprise stalks, stems, and cobs.…”

“…It has been confirmed that A. bisporus is a classical example of sustainable food production, which is cultured on compost made from agricultural waste products. The edible fungal compost production is a process involving the bioconversion of raw materials into a composted mixture, of which the temperature increases to 80 °C owing to thermophilic microorganisms ( Zhang et al, 2019 ). The activity of microorganisms alters the natural decomposition of lignocellulose in the compost of A. bisporus ( Jurak, Kabel & Gruppen, 2014 ).…”

“…In general, Phase I periods of about 5–7 and 15–21 days are used in Europe and China, respectively. The compost temperature stays at approximately 80 °C due to the growth of thermophilic microorganisms ( Zhang et al, 2019 ). Subsequently, a pasteurization process (Phase II) is performed at 45–50 °C for about 4–9 days until the ammonia level decreases to a level that is non-toxic to A. bisporus mycelia.…”

Growth-promoting thermophilic microorganisms in self-heating pasteurized substrate improve Agaricus bisporus mycelial growth

“…Oorschot & de Hoog (synonym Malbranchea sulfurea) and Myriococcum thermophilum (Fergus) Aa, which stimulate the mycelial growth and production of A. bisporus (Straatsma et al, 1991(Straatsma et al, , 1994Sánchez, 2007;Sánchez et al, 2008) by reducing the concentration of ammonium, immobilizing nutrients, and producing metabolites that can inhibit competing organisms. After the thermophilic fungi colonize the substrate at 45-50 °C, the substrate is cooled down (Zhang et al, 2019) and thermophiles diminish in activity or die and leave as residues their cell membranes, which are composed of polysaccharides, fatty acids such as linoleic acid and proteins that constitute a rich reserve for A. bisporus (Fermor and Wood, 1991). Alternative methods for substrate preparation without the generation of odor have been studied as an improvement of the traditional method of cultivation with two phases for the white button mushroom (Till, 1962;Sánchez and Royse, 2001;Bechara et al, 2005).…”