Integrated Method of Pretreatment, Saccharification and Electro-Fermentation of Saccharum Spontaneum to Produce Bioethanol Using Microbial Consortium

Abstract

Production of lignocellulosic ethanol using microbial consortium can be an economical strategy. Consortium of ligninolytic and cellulolytic microbe(s) that can depolymerize lignin and hydrolyze cellulose along with fermenting yeast (CDBT-2) can replace the separate techniques used for biomass pretreatment and hydrolysis prior to fermentation. So, the aim of this study was to screen fungi capable of producing laccase (lignin depolymerizing enzyme) and cellulase (converts cellulose to fermentable sugars), and use the strains along with Saccharomyces cerevisiae (CDBT-2) to develop an integrated method of simultaneous pretreatment saccharification and electro-fermentation of Saccharum spontaneum powder to produce ethanol. 18-s rRNA sequencing and BLAST analysis of screened isolates confirmed, cellulolytic isolate (F1) resembled as Aspergillus niger and, ligninocellulolytic isolate (F2) resembled to Ganoderma sessile. These fungi were used along with CDBT2 for ethanol production. Different consortiums sets of these isolates were tested for fermentation efficiency. All the analysis were done using crude untreated as well as hot water pretreated S. spontaneum powder to compare the ethanol production efficiency. In controlled environment of 28oC, shaking at 80 rpm and 5.0 pH, culture with consortium of G. sessile and CDBT2 produced higher ethanol with yield 57 mg/g biomass powder followed by consortium of G. sessile, A. niger and CDBT2 with yield of 44±0.18 mg/g biomass. Monoculture of G. sessile produced higher amount of phenol ie 292.48±17.74 µg/mL. Similarly, G. sessile, A. niger and CDBT2 consortium produced higher furfural of 58.48±3.86 µg/mL. However, the amount of phenol and furfural generated were very low in both cases. The ethanol yield was higher in crude biomass compared to hot water pretreated S. spontaneum powder. In addition, electro-fermentation of crude S. spontaneum enhanced ethanol production by 12% with G. sessile and CDBT2 consortium while 18% with the set of G. sessile, A. niger and CDBT2 consortium. This monophasic method of integrated pretreatment saccharification and electro-fermentation can be an alternative approach for lignocellulosic bioethanol production as it does not require separate pretreatment and fermentation approach.Keywords: Bioethanol, Saccharum spontaneum, microbial consortium, simultaneous saccharification and fermentation, and electro-fermentation Figure 1