Microwave-assisted cassava pulp hydrolysis as food waste biorefinery for biodegradable polyhydroxybutyrate production

Abstract

Cassava pulp is one of the most abundant agricultural residues that can cause serious disposal problems. This study aimed to apply a biorefinery approach by examining the feasibility of microwave-assisted cassava pulp hydrolysis to attain sustainable management and efficient use of natural resources. Four factors, namely, the liquid-to-solid ratio (20 mL/g, 10 mL/g, 7.5 mL/g, and 5 mL/g), types of acids (H2SO4 and H3PO4), watt power (600 W, 700 W, and 800 W) and time (3, 5 and 8 min), were carefully investigated. The highest fermentable sugar content of 88.1 g/L ± 0.7 g/L (0.88 g fermentable sugars/g dry cassava pulp) was achieved when 20 mL/g cassava pulp was hydrolyzed with 2.5% (v/v) H2SO4 under microwave irradiation at 800 W for 8 min. Glucose was a major product (82.0 g/L ± 5.2 g/L). The inhibitor concentration was 5.17 g/L ± 0.01 g/L, and the levulinic acid concentration was 5.15 g/L ± 0.01 g/L. The results indicated that the liquid-to-solid ratio, diluted acid concentration, irradiation watt power and time were important factors in producing fermentable sugars from acid hydrolysis under microwave irradiation. The crude hydrolysate was used for PHB production by Cupriavidus necator strain A-04. The hydrolysate to nutrients ratio of 30:70 (v/v) yielded a cell dry weight of 7.5 g/L ± 0.1 g/L containing PHB content of 66.8% ± 0.3% (w/w), resulting in a yield YP/S (g-PHB/g-SPHB) of 0.35 g/g. This study demonstrated that the microwave-assisted cassava pulp hydrolysate developed in this study provided a high amount of glucose (88.1% conversion) and resulted in a low concentration of inhibitors without xylose; this was successfully achieved without pregelatinization, alkaline pretreatment or detoxification.

Editorial: “The value of microbial bioreactors to meet challenges in the circular bioeconomy”

“…Another green extraction in the form of microwave-assisted hydrolysis on cassava pulp biomass waste for bioplastic (PHB) was performed by another research team ( Prasetsilp et al, 2023 ). Such a technique offers better radiation input and time and temperature control than alkaline and enzymatic treatments.…”

Valorization of agro-industrial waste from the cassava industry as esterified cellulose butyrate for polyhydroxybutyrate-based biocomposites

“…According to Matsui et al ( 2004), the chemical composition of CP varies between 40-60% starch, 15-50% cellulose, and other components, such as proteins and fat. Moreover, the compositions of the CP varied with changes in the species, cultivation location, cultivation conditions, harvest period and production process [28].…”

“…As a result, it starts to spoil right away and gives off an offensive odor and pollutes ground water. According to previous reports, cassava pulp contains 40%-80% starch and 20%-40% fibers depending on the starch milling technology, plant variety and other environmental factors [28][29][30]. Sinsukudomchai et al studied a green composite made of PHB and long-chain fatty acid esterified microcrystalline cellulose from pineapple leaf (esterified PALF-MCC laurate).…”

Minimization of Inhibitor Generation in Rice Straw Hydrolysate Using RSM Optimization Technique

“…These inhibitors must be controlled and reduced to a minimum level during the process to achieve the sustainable production of precursor fermentable sugar molecules for ethanol production. The factors responsible for inhibitor production include reaction temperature, acid concentration, autoclave time, and solid biomass concentration [12]. Studies have shown that pretreatment of solid biomass with high acid and temperature generates higher concentrations of degradation products like furfural and HMF, with an improved chance of fermentable sugar yield from the process [13].…”