Evaluation of Preparation and Detoxification of Hemicellulose Hydrolysate for Improved Xylitol Production from Quinoa Straw

Preparation and Immobilization Mechanism on a Novel Composite Carrier PDA-CF/PUF to Improve Cells Immobilization and Xylitol Production

The preparation of a novel composite carrier of polydopamine-modified carbon fiber/polyurethane foam (PDA-CF/PUF) was proposed to improve cell immobilization and the fermentation of xylitol, which is an important food sweetener and multifunctional food additive. Candida tropicalis was immobilized on the composite carrier by adsorption and covalent binding. The properties and immobilization mechanism of the composite carrier and its effect on immobilized cells were investigated. It showed that the modification of PDA enhanced the loading of CF on the PUF surface and the adhesion of cells on the composite carrier surface. Also, the biocompatibility of carriers to cells was improved. In addition, the introduction of PDA increased the active groups on the surface of the carrier, enhanced the hydrophilicity, promoted the cells immobilization, and increased the xylitol yield. It was also found that expression of the related gene XYL1 in cells was significantly increased after the immobilization of the PDA-CF/PUF composite carrier during the fermentation. The PDA-CF/PUF was an immobilized carrier with the excellent biocompatibility and immobilization performance, which has great development potential in the industrial production of xylitol.

Detoxification Approaches of Bagasse Pith Hydrolysate Affecting Xylitol Production by Rhodotorula mucilaginosa

In this study, the potential of bagasse pith (the waste of sugar and paper industry) was investigated for bio-xylitol production for the first time. Xylose-rich hydrolysate was prepared using 8% dilute sulfuric acid, at 120 °C for 90 min. Then, the acid-hydrolyzed solution was detoxified by individual overliming (OL), active carbon (AC), and their combination (OL+AC). The amounts of reducing sugars and inhibitors (furfural and hydroxyl methyl furfural) were measured after acid pre-treatment and detoxification process. Thereafter, xylitol was produced from detoxified hydrolysate by Rhodotorula mucilaginosa yeast. Results showed that after acid hydrolysis, the sugar yield was 20%. Detoxification by overliming and active carbon methods increased the reducing sugar content up to 65% and 36% and decreased the concentration of inhibitors to >90% and 16%, respectively. Also, combined detoxification caused an increase in the reducing sugar content (>73%) and a complete removal of inhibitors. The highest productivity of xylitol (0.366 g/g) by yeast was attained after the addition of 100 g/l non-detoxified xylose-rich hydrolysate into fermentation broth after 96 h, while the xylitol productivity enhanced to 0.496 g/g after adding the similar amount of xylose-rich hydrolysate detoxified by combined method (OL+AC2.5%).

Microbial alchemy: upcycling of brewery spent grains into high-value products through fermentation

Spent grains are one of the lignocellulosic biomasses available in abundance, discarded by breweries as waste. The brewing process generates around 25-30% of waste in different forms and spent grains alone account for 80-85% of that waste, resulting in a significant global waste volume. Despite containing essential nutrients, i.e., carbohydrates, fibers, proteins, fatty acids, lipids, minerals, and vitamins, efficient and economically viable valorization of these grains is lacking. Microbial fermentation enables the valorization of spent grain biomass into numerous commercially valuable products used in energy, food, healthcare, and biomaterials. However, the process still needs more investigation to overcome challenges, such as transportation, cost-effective pretreatment, and fermentation strategy. to lower the product cost and to achieve market feasibility and customer affordability. This review summarizes the potential of spent grains valorization via microbial fermentation and associated challenges.

Physicochemical Pretreatment of Vietnamosasa pusilla for Bioethanol and Xylitol Production

The consumption of fossil fuels has resulted in severe environmental consequences, including greenhouse gas emissions and climate change. Therefore, transitioning to alternative energy sources, such as cellulosic ethanol, is a promising strategy for reducing environmental impacts and promoting sustainable low-carbon energy. Vietnamosasa pusilla, an invasive weed, has been recognized as a high potential feedstock for sugar-based biorefineries due to its high total carbohydrate content, including glucan (48.1 ± 0.3%) and xylan (19.2 ± 0.4%). This study aimed to examine the impact of NaOH pretreatment-assisted autoclaving on V. pusilla feedstock. The V. pusilla enzymatic hydrolysate was used as a substrate for bioethanol and xylitol synthesis. After treating the feedstock with varying concentrations of NaOH at different temperatures, the glucose and xylose recovery yields were substantially higher than those of the untreated material. The hydrolysate generated by enzymatic hydrolysis was fermented into bioethanol using Saccharomyces cerevisiae TISTR 5339. The liquid byproduct of ethanol production was utilized by Candida tropicalis TISTR 5171 to generate xylitol. The results of this study indicate that the six- and five-carbon sugars of V. pusilla biomass have great potential for the production of two value-added products (bioethanol and xylitol).