Pretreatment of finger millet straw (Eleusine coracana) for enzymatic hydrolysis towards bioethanol production

To obtain high yields of products through bioconversion processes, biomass must be pretreated to change its recalcitrant structures. The key goal of this analysis is to compare the findings in terms of total reducing sugar yield after organic solvents and hot water pretreatment on finger millet straw (FMS) using laboratory-scale equipment. Accordingly, the effect of two separate pretreatments, i.e., liquid hot water, and organic solvent (ethanol) at autoclave, and furnace temperatures, was investigated in this study to increase the enzymatic conversion of FMS under optimal conditions. The biomass recovery was found highest under the liquid hot water (autoclave; 9.477 +/- 0.017%) pretreatment conditions. In addition, the cellulose content improved significantly with pretreatment, increasing from 41.7 +/- 0.74 to 55.33 +/- 0.89%, while the hemicellulose and lignin contents significantly decreased. The untreated sample having a lignin amount of around 6.42 +/- 0.21% after different pretreatment methods dropped significantly (p = 0.00737**) and was found to have a 39.8 +/- 1.84% delignification rate based on the ethanol autoclave method. The findings of the study revealed that the FMS is severely affected by liquid hot water and organic solvent pretreatment in the autoclave than the furnace. After the pretreatment procedure, the maximum amount of crystalline cellulose in biomass was transformed to the amorphous state, as shown by the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The pretreated cellulase blend enzyme sample was most active on the biomass treated with 1:20% (w/v) liquid hot water combined with autoclave heating at 121 degrees C, with 15 psi for 20 min, resulting in highest total reducing sugars; thus, results showed that the pretreated sample (0.75 g) contains 60.94 mg/g of fermentative sugars based on a 15% (w/v) ratio which claimed to be the fact that this is a better result than any other research by using FMS.

Automated summary

This study compares the effects of organic solvent and hot water pretreatment on the total reducing sugar yield of finger millet straw biomass. The results show that the highest biomass recovery and increase in cellulose content were achieved with liquid hot water pretreatment, while hemicellulose and lignin contents significantly decreased.