Waste-reducing cultivation of Pleurotus ostreatus and Pleurotus pulmonarius on coffee pulp: changes in the production of some lignocellulolytic enzymes

Fruiting body production for one strain of Pleurotus ostreatus and three strains of P. pulmonarius was evaluated on coffee pulp pasteurized at 80 °C for 1 h. Based upon three harvests per strain, the single P. ostreatus line was found to display a 40-day culture cycle, whereas the three P. pulmonarius strains completed their cycles after more than 50 days of incubation. These time periods were notably shorter than those observed in previous studies using other growth substrates. Nevertheless, yields expressed as biological efficiencies were not significantly different among strains, fluctuating between 125 and 138%. Extracellular enzymatic activity was also monitored for P. ostreatus and P. pulmonarius (one strain only). To do this, samples of mycelium-bearing substrate were taken every 4 days throughout the incubation period. Care was taken to represent all developmental stages, including primordial and fruiting bodies. Samples were either lyophilized and then analysed or, in some cases, analysed immediately without lyophilization. Hydrolase activity (i.e. endoglucanase (CMC) and cellobiohydrolase (CBH)) was found to depend on developmental stage, showing peak production during fruiting body formation. On the other hand, oxidase activity-(i.e. laccase (LAC) and Mn-peroxidase (MnP)) was associated with phenol degradation. Nevertheless, in the case of oxidases developmental timing differences were also observed. Specifically, LAC activity was detected as early as 8 days after inoculation in non-lyophilized samples, whereas MnP appeared near the end of the incubation period. No LAC activity was observed in lyophilized samples. This study concludes that coffee pulp might be successfully employed in the cultivation of mushrooms, not only because important extracellular enzymes are produced by mushrooms when grown upon this substrate, but also because the abbreviated cultivation cycle associated with this medium favours commercial processes. Commercialization might be further improved if strains specifically adapted to this novel substrate are selected.