Cultivating Pleurotus ostreatus and Pleurotus eryngii mushroom strains on agro-industrial residues in solid-state fermentation. Part I: Screening for growth, endoglucanase, laccase and biomass production in the colonization phase

Abstract

The influence of ten agro-residues, i.e., wheat straw (WS), poplar wood sawdust (PWS), grape pomace (GP), beech wood shavings (BWS), cotton cake (CK), corn cobs (CC), coffee residue (CR), olive pulp (OP), barley and oats straw (BOS) and rice bark (RB), used as alternative substrates for the cultivation of Pleurotus mushrooms, was examined during mycelial growth (colonization phase). Several native and commercial strains of P. ostreatus and P. eryngii were subjected to screening regarding their mycelial growth rates, biomass production and endoglucanase and laccase activities. The experimental results showed that the highest growth rates of P. ostreatus strains were noticed on BWS, BOS, CC and RB substrates, with the time of complete colonization varying between 16 and 36 days, whereas for P. eryngii a high linear growth rate was observed on CC, OP, CR and BOS with the colonization period ranging between 26 and 51 days. The maximum biomass production obtained on the various substrates for both Pleurotus species ranged from 115.32 to 454.42 mg/g d.w. for P. ostreatus and from 108.50 to 422.59 mg/g d.w. for P. eryngii. As for endoglucanase, the highest activities were observed in P. eryngii AMRL 163 cultures on PWS and BOS, i.e., 0.19 and 0.18 U/g d.w., respectively. P. eryngii AMRL 173–6 and P. ostreatus AMRL 150 cultivated on RB and BOS, synthesized significant laccase amounts, i.e., 2172.28 and 1987.25 U/g d.w., respectively. The effect of the substrate components on the growth parameters was considered and discussed. This study showed the industrial potential to convert important low-value agro-residues to fungal biomass and enzymes and eventually to valuable food products.