Abstract
By cultivating a strain of Aspergillus tubingensis on agro-industrial by-products using solid-state fermentation technology, a biocatalyst containing more than 130 different enzymes was obtained. The enzymatic complex was composed mainly of hydrolases, among which a protease, an aspergillopepsin, accounted for more than half of the total proteins. Cell-wall-degrading enzymes such as pectinases, cellulases and hemicellulases were also highly represented. Adding the biocatalyst to corn mash at 1 kg/T corn allowed to significantly improve ethanol production performances. The final ethanol concentration was increased by 6.8% and the kinetics was accelerated by 14 h. The aim of this study was to identify the enzymes implicated in the effect on corn ethanol production. By fractionating the biocatalyst, the particular effect of the major enzymes was investigated. Experiments revealed that, together, the protease and two cellulolytic enzymes (an endoglucanase and a β-glucosidase) were responsible for 80% of the overall effect of the biocatalyst. Nevertheless, the crude extract of the biocatalyst showed greater impact than the combination of up to seven purified enzymes, demonstrating the complementary enzymatic complex obtained by solid-state fermentation. This technology could, therefore, be a relevant natural alternative to the use of GMO-derived enzymes in the ethanol industry.
Highlights
The use of solid-state fermentation technology to produce industrial enzymes is common in eastern countries such as India, China or Japan, and has been of growing interest for numerous applications worldwide over the past few decades (Bhargav et al 2008; Brahmachari 2017; Subramaniyam and Vimala 2012)
The strain and blend of substrates were selected based on previous experiments
Enzymatic assays confirmed that the crude extract contained high levels of protease, pectinase, cellulase and xylanase activity (Table 1)
Summary
The use of solid-state fermentation technology to produce industrial enzymes is common in eastern countries such as India, China or Japan, and has been of growing interest for numerous applications worldwide over the past few decades (Bhargav et al 2008; Brahmachari 2017; Subramaniyam and Vimala 2012). This technology can be used with a wide range of microorganisms, including fungi, yeasts and bacteria. The addition of enzymes is essential in the biochemical conversion of starchy and lignocellulosic biomass into fuel ethanol. Starch-to-ethanol processes are already efficient, numerous recent works have evidenced
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