Degradation of rice straw by Pleurotus flabellatus

Abstract

A BS TRA CTDegradative changes in the constituents of rice straw substrate during the growth and commercialproduction of fruit bodies by Pleurotus flabellatus were investigated. There was a continuous increase in the free sugars from the time of inoculation until the end of harvesting of the fruit bodies, whereas the free amino acids reached a maximum at the end of mycelial growth and showed a slight decrease after fructification. Glucose, xylose, arabinose, cellobiose and a higher oligosaccharide represented the spectrum of sugars produced. Of the 12 amino acids (apart from two peptides) identified, aspartic acid, histidine and tyrosine were the major components, Solubilities and spectral characteristics of lignin degraded in the straw substrate were studied using alkali-extracted lignin. Laccase and protease activities in the straw substrate at different stages of fungal 'degradation could be correlated to the decreases in the staw lignin and protein contents, respectively. Colour reactions of the fungus on several phenolic media, demonstration of phenolic oxidases in the straw substrate, and ability of the fungus to degrade lignin conclusively proved that the fungus under study is a typical 'white rot' fungus. Degradation of the straw substrate by the fungus reached a maximum at the end of harvest of the fruit bodies. The spent straw substrate (left over after harvesting the fruit bodies) contained free sugars and amino acids, respectively 5 and 2 times the concentration of those in the undegraded straw substrate, and lignin decreased to about 25% of the level in the straw before fermentation. Potential applications of the spent straw substrate as an upgraded form of rumen feed and for the production of single-cell protein are discussed.

Lignocellulolytic enzyme activity, substrate utilization, and mushroom yield by Pleurotus ostreatus cultivated on substrate containing anaerobic digester solids

“…Our results are consistent with the findings of Rajarathnam et al [36], who reported that laccase reached maximum activity at the beginning of fructification and decreased thereafter. However, by comparing laccase and peroxidase enzyme activities (Table 4) with lignin degradation (Fig.…”

Bioconversion and biotransformation of coir pith for economic production of Pleurotus florida: chemical and biochemical changes in coir pith during the mushroom growth and fructification

“…Using this culture, spawn was prepared on cooked jowar (Sorghum vulgare) grains, fortified with 2% calcium carbonate, under aseptic conditions (Rajarathnam and Zakia Bano 1987). A 20-day-old grain spawn was used for inoculating the coir pith substrate.…”

“…Acetone powders were used for the measurement of laccase and protease activities (Rajarathnam et al 1987). Twenty-five grams of fresh samples were homogenized in a minimum volume of sodium phosphate buffer (50 mM, pH 6.5) so as to obtain slurry.…”

Influência da composição química do substrato no cultivo de Pleurotus florida

“…A degradação da lignina é um pré-requisito para acessar com facilidade a degradação da celulose e hemicelulose (RAJARATHNAM et al, 1979, RAJARATHNAM et al, 1987. Além disso, a lignina juntamente com a hemicelulose, envolve as fibras de celulósicas, formando uma barreira física que dificulta a atividade das enzimas celulolíticas, restringindo o ataque à superfície externa do substrato (RAJARATHNAM et al, 1998).…”

“…Os resultados de produção observados com palha de feijão foram semelhantes à palha de arroz, resíduo tradicionalmente utilizado na produção comercial de Pleurotus (RAJARATHNAM et al, 1987). Além disso, a composição química favorável da palha de feijão e a tecnologia de cultivo simples empregada nesse experimento evidenciam que esse substrato é viável para o cultivo de P. florida.…”