Cost-effective valorization of cassava fibrous waste into enantiomerically pure D-lactic acid: Process engineering and kinetic modelling approach

Abstract

Cassava fibrous waste (CFW) valorization on the synthesis of D (-) lactic acid (DLA) holds enormous importance, particularly in the production of thermostable and biodegradable polymers. In this study, microbial kinetic modelling was carried out to investigate the dynamics of cassava fibrous waste enzyme hydrolysate (CFWEH) utilization towards DLA production. Designed biomass approach was attempted to evaluate the natural DLA producing organisms, capable of metabolizing CFWEH into optically pure DLA. Sporolactobacillus inulinus (NBRC 13595) was found to be the elite strain, resulting the yield of 99.43 % optically pure DLA using CFWEH-supplemented medium. Yeast extract (2 gL −1 ) was observed to be potential nitrogen source over other complex nitrogen sources for kinetic modelling investigation. Kinetic parameters predicted from the proposed model for DLA production showed maximum specific growth rate, μ max - 0.36 (h −1 ); growth-associated product coefficient ( α = 0 . 47 gg −1 ) and specific productivity ( q P , m a x = 1 . 12 gg −1 h −1 ) respectively. Experimental data of biomass growth, substrate consumption and DLA production with initial sugar concentrations ranging from 20–180 gL −1 was found to be synchronized well with the simulated dynamic profiles. Kinetic investigation reported in this study is a novice attempt enumerating the valorization potential of CFW for the synthesis of value-added products including DLA at commercial scale in near future. • High optical purity (99.43 %) was achieved for D-Lactic Acid. • Valorization potential of cassava fibrous waste was elucidated. • First kind of study on kinetic modelling, utilizing cassava fibrous waste. • Potential scope for techno-economic feasibility of cassava fibrous waste.