Solid state fermentative lignocellulolytic enzymes production, characterization and its application in the saccharification of rice waste biomass for ethanol production: An integrated biotechnological approach

Abstract

This work evaluates lignocellulolytic enzymes production by a selected strain Streptomyces sp. MDS cultivated in various agricultural wastes under solid-state fermentation (SSF). Maximum activities (U/gds) of endoglucanase (132.6 ± 1.15), exoglucanase (14.6 ± 0.62), cellobiase (125.6 ± 1.75), filter paperase (19.7 ± 0.42), amylase (278.5 ± 3.53), and xylanase (342.5 ± 3.36) were produced with rice waste biomass (RWB). Operational parameters and supplementation of nitrogen sources, metal additives, and surfactants were systematically optimized with a view to maximizing enzyme production. The harvested enzyme exhibited good stability at high pH (5 to 8) and temperature (50 to 80 °C) and showed robust nature in the presence of organic solvents, surfactants, and commercial detergents. The potential of crude enzyme mixture for hydrolysis of mild alkaline pretreated RWB was demonstrated, resulting in equivalent saccharification (64.85 ± 1.11%) relative to commercial enzymes (69.41 ± 1.15%). Yeast co-culture of Saccharomyces cerevisiae and Kluyveromyces marxianus resulted in higher ethanol production (21.12 ± 0.82 g/L) and sugar consumption (88%) from enzymatic RWB hydrolysates (50 g/L) than monoculture. Finally, the leftover spent slurry from SSF effectively decolorized individual dyes and the actual textile wastewater, which increases the practical applicability of the developed bioprocess.