Production of α-amylase under solid-state fermentation utilizing coffee waste

Coffee industry substrates such as coffee pulp, coffee cherry husk, silver skin, spent coffee and mixtures of these coffee wastes (MC) were evaluated for their efficacy as sole carbon source for the synthesis of alpha-amylase in solid-state fermentation (SSF) using a fungal strain of Neurospora crassa CFR 308. For SSF with coffee pulp and with MC, alpha-amylase activity of 3908 U g(-1) ds (units per gram of dry substrate) and 3870 U g(-1) ds, respectively, was observed. Parameters such as moisture (60%), pH (4.6), temperature (28 degrees C), particle size (1.0 mm), inoculum size (107 spores g(-1) ds), and fermentation time (5 days) were optimized for enzyme synthesis, wherein 4981 and 4324 U g(-1) U g(-1) ds of alpha-amylase activity was obtained in SSF with coffee pulp and MC, respectively. The enzyme production was further improved when the substrates were subjected to pre-treatment by steaming. Accordingly, maximum alpha-amylase activity of 7084 U g(-1) ds and 6342 U g(-1) ds was obtained with steam-pretreated coffee pulp and MC, respectively, demonstrating them to be excellent sole carbon sources for synthesis of alpha-amylase production. (C) 2009 Society of Chemical Industry