Substrate-related factors and kinetic studies of Carbohydrate-Rich food wastes on enzymatic saccharification

Food waste biorefinery is a sustainable approach to producing green chemicals, however the essential substrate-related factors hindering the efficacy of enzymatic hydrolysis have never been clarified. This study explored the key rate-limiting parameters and mechanisms of carbohydrate-rich food after different cooking and storing methods, i.e., impacts of compositions, structural diversities, and hornification. Shake-flask enzymatic kinetics determined the optimal dosages (0.5 wt% glucoamylase, 3 wt% cellulase) for food waste hydrolysis. First order kinetics and simulation results determined that reaction coefficient (K) of cooked starchy food was ∼ 3.63 h-1 (92 % amylum digestibility) within 2 h, while those for cooked cellulosic vegetables were 0.25-0.5 h-1 after 12 h of hydrolysis. Drying and frying reduced ∼ 71-89 % hydrolysis rates for rice, while hydrothermal pretreatment increased the hydrolysis rate by 82 % on vegetable wastes. This study provided insights into advanced control strategy and reduced the operational costs by optimized enzyme doses for food waste valorization.

Comparison of the substrate enzymatic digestibility and lignin structure of wheat straw stems and leaves pretreated by green liquor

In this work, the substrate enzymatic digestibility (SED) and the lignin structure of green liquor (GL) pretreated wheat straw stems and leaves were investigated. Compared with wheat straw stems, leaves showed higher delignification selectivity in GL pretreatment and higher SED in enzymatic hydrolysis. Wet chemical analysis indicated that, characterized with lower content of syringyl units and less β-O-4 linkages, leaf lignin is structurally different from stem lignin. After GL pretreatment, the drops of both nitrobenzene oxidation and ozonation products yield of leaves were obviously higher than those of stems, which means that more β-O-4 linkages of leaf lignin were broken than that of stem lignin. The SED of total sugar in GL-pretreated leaves was about 50% higher than that in GL-pretreated stems. The less content and lower S/G ratio of lignin are suggested to be the important factors for the better SED of GL-pretreated leaves.