Analysis of thermophilic fungal populations during phase II of composting for the cultivation of Agaricus subrufescens

Abstract

The composition and genetic diversity of fungal populations during phase II of compost production for the cultivation of Agaricus subrufescens was determined using culture-dependent and -independent methods on days 3, 6, 10, 12, and 14 of phase II composting. The isolates were morphologically characterized and subsequently analyzed using repetitive extragenic palindromic sequences (rep-PCR), and the intergenic region was sequenced to genetically identify the isolates. Changes on in the filamentous fungi population were analyzed using denaturing gradient gel electrophoresis (DGGE), and the resulting bands were sequenced. The population did not significantly change from day 3 to 10 (2.55 x 10(5) -6 x 10(5) CFU g(-1)), and maximum counts on day 14 of phase II composting (6.92 log CFU g(-1)). In the morphological characterization, Scytalidium thermophilum, Thermomyces lanuginosus, and Thermomyces ibadanensis were the most abundant identified species. The 26 most abundant isolates identified by morphological analysis were characterized using rep-PCR. A significant amount of genetic diversity was detected among the isolates of all three studied species. Based on the DGGE analysis, the diversity of the fungi was reduced during phase II composting, and S. thermophilum was the predominant species identified throughout the entire process. Thus, this study presents the first report of the involvement of T. ibadanensis in the production of compost for Agaricus mushroom cultivation.

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

“…It agrees with previous criteria and experiences that used pasteurized substrates by self-heating for the cultivation of Pleurotus spp., A. bisporus and other edible mushrooms (Morales and Sánchez, 2017;Colmenares et al, 2017). The data regarding the population dynamics of thermophilic microorganisms in pangola grass pasteurized by self-heating varied between 2.6x10 4 -4.6x10 8 CFU g -1 at 45 °C and 2.3x10 5 -6.5x10 8 CFU g -1 at 55 °C, similar to what was reported by Souza et al (2014), who in a study of thermophilic population diversity during phase II of composting for the cultivation of A. subrufescens found densities of 2.55x10 5 -6x10 5 CFU g -1 . These quantities are related to temperature profile, nutrient availability, oxygen concentration, moisture content and pH (Camacho et al, 2014), in addition to the availability of carbon produced by the degradation of lignin associated with the cellulose and hemicellulose of the substrates used (Wood, 1984).…”

“…Agaricus bisporus is commercially cultivated on organic materials such as wheat straw, manure, and corncob, requiring an important treatment including composting and pasteurization to produce a selective substrate that promotes the mycelial growth and fruiting of mushrooms (Song et al, 2014). The composting process occurs naturally as a consequence of the microbial activity on the wet raw material and is considered essential to develop the final quality of the compost (Souza et al, 2014). Due to the microbial metabolism of sugars, the temperature inside the compost increases, and the mesophilic microbiota is replaced by the thermophilic microbiota.…”

Microbial additives in the composting process

“…The composting of organic residues is a natural process in which microorganisms will convert biodegradable organic matter into a final compost, humus, which will be able to be utilized in several sectors of agriculture (Souza et al, 2014). A large number of factors are responsible for the final quality and stability of the product, such as temperature, moisture, pH, nitrogen and particle size (Wong et al, 2011;Zhang et al, 2012).…”

Using of Appropriated Strains in the Practice of Compost Supplementation for Agaricus subrufescens Production

“…Among the different steps of production, compost (formulation, phase I and II) is thought to be one of the most important, because it directly influences the productivity and quality of the mushrooms (Horm and Ohga, 2008;Matute et al, 2010;Llarena-Hernández et al, 2013;Wang J. T. et al, 2013;Souza et al, 2014). To improve the compost process, substrate supplementation has been used to provide nutrients to the developing mushroom, reducing the cultivation cycle and increasing productivity by up to 30% .…”