Effect of caffeine and tannins on cultivation and fructification of Pleurotus on coffee husks

Abstract

The objective of this work was to study the effect of caffeine and tannins on Pleurotus sp. cultivation and to evaluate the feasibility of using coffee husks as substrate for mushroom cultivation. Eight strains of P. ostreatus and two strains of P. sajor-caju were screened on a medium prepared from agar extract of coffee husk. Based on best mycelial growth and biomass production, the strain P. ostreatus LPB 09 was selected for detailed studies. With the increase of caffeine concentration, the mycelial growth and the biomass production decreased, and no growth was observed when concentration of caffeine was 2500 mg/L. Furthermore, Pleurotus did not degrade the caffeine, but absorbed it. Tannin under 100 mg/L in the medium stimulated the growth of mycelia, but above 500 mg/L it had a negative effect. When the concentration reached 1000 mg/L, the fungus still survived and showed a certain tolerance to it. No tannic acid was found in the mycelia, but its concentration decreased in the medium. This fact confirmed that Pleurotus had the capacity of degrading tannic acid. Fructification occurred after 20 days of inoculation and the biological efficiency reached about 97% after 60 days. Caffeine content in the husk after cultivation was reduced to 60.7% and tannins to 79.2%. The results indicated the feasibility of using coffee husk without any pretreatment for the cultivation of Pleurotus.