Bioprocess development of 2, 3-butanediol production using agro-industrial residues.

The valorization of agricultural and industrial wastes for fuel and chemical production benefits environmental sustainability. 2, 3-Butanediol (2,3-BDO) is a value-added platform chemical covering many industrial applications. Since the global market is increasing drastically, production rates have to increase. In order to replace the current petroleum-based 2,3-BDO production, renewable feedstock's ability has been studied for the past few decades. This study aims to find an improved bioprocess for producing 2,3-BDO from agricultural and industrial residues, consequently resulting in a low CO2 emission bioprocess. For this, screening of 13 different biomass samples for hydrolyzable sugars has been done. Alkali pretreatment has been performed with the processed biomass and enzyme hydrolysis performed using commercial cellulase. Among all biomass hydrolysate oat hull and spruce bark biomass could produce the maximum amount of total reducing sugars. Later oat hull and spruce bark biomass with maximum hydrolyzable sugars have been selected for submerged fermentation studies using Enterobacter cloacae SG1. After fermentation, 37.59 and 26.74 g/L of 2,3-BDO was obtained with oat hull and spruce bark biomass, respectively. The compositional analysis of each step of biomass processing has been performed and changes in each component have been evaluated. The compositional analysis has revealed that biomass composition has changed significantly after pretreatment and hydrolysis leading to a remarkable release of sugars which can be utilized by bacteria for 2,3-BDO production. The results have been found to be promising, showing the potential of waste biomass residues as a low-cost raw material for 2,3-BDO production and thus a new lead in an efficient waste management approach for less CO2 emission.

Addressing challenges in production of cellulases for biomass hydrolysis: Targeted interventions into the genetics of cellulase producing fungi.

Lignocellulosic materials are the favoured feedstock for biorefineries due to their abundant availability and non-completion with food. Biobased technologies for refining these materials are limited mainly by the cost of biomass hydrolyzing enzymes, typically sourced from filamentous fungi. Therefore, considerable efforts have been directed at improving the quantity and quality of secreted lignocellulose degrading enzymes from fungi in order to attain overall economic viability. Process improvements and media engineering probably have reached their thresholds and further production enhancements require modifying the fungal metabolism to improve production and secretion of these enzymes. This review focusses on the types and mechanisms of action of known fungal biomass degrading enzymes, our current understanding of the genetic control exerted on their expression, and possible routes for intervention, especially on modulating catabolite repression, transcriptional regulators, signal transduction, secretion pathways etc., in order to improve enzyme productivity, activity and stability.

Evaluation of a wet processing strategy for mixed phumdi biomass conversion to bioethanol.

Biorefineries typically use dry feedstock due to technical and logistic issues, but in unique cases where climatic conditions are unfavorable and where the biomass has to be processed without a holding time, wet processing might be advantageous. The present study evaluated the possibility of using the fresh (non-dried) mixed biomass harvested from Phumdis; which are floating vegetation unique to Loktak lake in Manipur, India, for bioethanol production. Pretreatment with dilute alkali (1.5% at 120 °C for 60 min) resulted in 36% lignin removal and an enhancement of cellulose content to 48% from 37%, and enzymatic hydrolysis released 25 g/L glucose. Fermentation of the hydrolysates was highly efficient at 95%, attained in 36 h and 80% in just 12 h. The new wet processing strategy could help in value addition of mixed phumdi biomass.