Combined Effect of Spent Mushroom Substrate and Agro-Industrial Residues on Pleurotus columbinus Production and Intra-Cellular Polysaccharide Synthesis

Spent mushroom substrate (SMS), spent coffee grounds from espresso production (SCG), faba bean harvest residues (FBR), pistachio shells (PS) wheat straw (WS) (control) agro-industrial waste were combined in different ratios, with or without supplements (wheat bran, soybean flour), to create novel substrates for <i>Pleurotus columbinus</i> growth. The impact of the substrates on the mycelial growth rate (Kr), biomass production, laccase, total cellulases and carbohydrate synthesis, along with the C and N consumption by <i>P. columbinus</i>, were examined in fully colonized substrates. The incubation period, earliness and biological efficiency (B.E.) (%) were also determined. Then, the intracellular polysaccharide (ICP) contents of the <i>P. columbinus</i> produced mushrooms were evaluated in the most promising substrates. <i>P. columbinus</i> was grown successfully in a wide range of C/N ratios of substrates and the fastest Kr (7.6 mm/d) was detected on the 70 SMS-30 FBR, without supplements, whereas substrates consisting of SCG enhanced biomass production (700.0-803.7 mg/g d.w.). SMS and PS or SCG led to the shortest incubation and earliness period of <i>P. columbinus</i>. The C content was reduced and the N content was substantially increased in all the colonized substrates. The 70 SMS-30 FBR and 80 SMS considerably enhanced the laccase production (up to 59,933.4 U/g d.w.) and substrates consisting of PS promoted total cellulases activities. Greater amounts of carbohydrates (3.8-17.4 mg/g d.w.) than that in the control were recorded for all the substrates. The combination of SMS and SCG or WS led to the highest B.E. values (59.3-87.1%) and ICP amounts (34.7-45.9%, <i>w</i>/<i>w</i>), regardless of the supplement addition. These findings support the effective utilization of agro-industrial waste in <i>P. columbinus</i> cultivation, producing high-value-added compounds and supporting mushroom growth.