Ethanol production from agroindustrial biomass using a crude enzyme complex produced by Aspergillus niger

Abstract

This study investigates ethanol production from simultaneous fermentation and saccharification (SFS) and separated hydrolysis and fermentation (SHS) using enzyme complexes produced by Aspergillus niger strains (ATCC 16404, ATCC 1057, ATCC 9029). The enzyme complexes were produced by solid-state fermentation (SSF) on inexpensive and readily available agroindustrial products: rice byproduct (composed of AFEX-treated rice rust and rice bran), whey and sugarcane bagasse. The ethanol was produced by Saccharomyces cerevisiae Y904 using whey and rice byproduct as the substrate and the enzyme complex produced by A. niger. The best result for solid-state fermentation (40 U/g of dry substrate, A. niger ATCC 16404) was obtained in a 0.5 L rotating drum bioreactor at 40 °C filled half filled with solid biomass composed of rice byproduct (86% wt/wt), whey (12% wt/wt) and CaCl2 (2.0% wt/wt). The best result for ethanol fermentation (11.7 g/L of ethanol) was obtained after 12 h of SFS at pH 4.5 and 35 °C. A comparative study of ethanol production by Trichoderma reesei CCT 2768 and A. niger ATCC 16404 complexes under the same optimised SFS and SSF conditions was also performed, revealing that ethanol production by the A. niger enzyme complex was 2.25 times higher than that by T. reesei. These findings suggest that the ethanol production using crude enzymatic complexes produced by A. niger and agroindustrial biomass described in this paper is very promising in terms of disposal of the whey produced by cheese-making and other dairy food processing.