Substratum formulation for laccase and mycelial biomass production of Pleurotus ostreatus

Abstract

Pleurotus ostreatus is a producer of biomass and laccase, an enzyme used in fermentation processes for the hydrolysis of lignocellulosic substrate, with potential use in biofuel production and animal feed. Thus, there is a need to seek more appropriate regional substrate for the production of mycelial biomass and laccase. Hence, the aim of this study was to evaluate the effect of physical and chemical characteristics of agro-industrial byproducts in a substratum formulation for the mycelial growth and laccase production by P. ostreatus. The experiment was conducted with the milled raw materials: soy fiber, wheat bran, rice bran, corn grain and corn cob that were separated according to size and analyzed for carbon/nitrogen (C/N) ratio. Mycelial growth was evaluated on substratum in cylindrical tubes of borosilicate. Then laccase production was assessed using a 26-2 fractional factorial design with the variables: raw material granulometry and addition of minerals (copper, zinc, iron, cadmium and magnesium) in the substrate. The production of laccase was determined by oxidation of ABTS (2,2’-bisazin-(3-ethylbenzothiazoline-6-sulfonic acid). The results indicate that the most important factor for mycelial growth is the holding capacity of oxygen in the substratum. For mycelial growth of P. ostreatus the corn cob and wheat bran are the best components for the substrate. The other raw materials reduced the mycelial growth. However the most important factor for the induction of laccase production is the reduction of particle size, increasing the contact area between the mycelium and the substratum.