Relation of xylitol formation and lignocellulose degradation in yeast.

One of the critical steps of the biotechnological production of xylitol from lignocellulosic biomass is the deconstruction of the plant cell wall. This step is crucial to the bioprocess once the solubilization of xylose from hemicellulose is allowed, which can be easily converted to xylitol by pentose-assimilating yeasts in a microaerobic environment. However, lignocellulosic toxic compounds formed/released during plant cell wall pretreatment, such as aliphatic acids, furans, and phenolic compounds, inhibit xylitol production during fermentation, reducing the fermentative performance of yeasts and impairing the bioprocess productivity. Although the toxicity of lignocellulosic inhibitors is one of the biggest bottlenecks of the biotechnological production of xylitol, most of the studies focus on how much xylitol production is inhibited but not how and where cells are affected. Understanding this mechanism is important in order to develop strategies to overcome lignocellulosic inhibitor toxicity. In this mini-review, we addressed how these inhibitors affect both yeast physiology and metabolism and consequently xylose-to-xylitol bioconversion. In addition, this work also addresses about cellular adaptation, one of the most relevant strategies to overcome lignocellulosic inhibitors toxicity, once it allows the development of robust and tolerant strains, contributing to the improvement of the microbial performance against hemicellulosic hydrolysates toxicity. KEY POINTS: • Impact of lignocellulosic inhibitors on the xylitol production by yeasts • Physiological and metabolic alterations provoked by lignocellulosic inhibitors • Cell adaptation as an efficient strategy to improve yeast's robustness.

The Prospering of Macromolecular Materials Based on Plant Oils within the Blooming Field of Polymers from Renewable Resources.

This paper provides an overview of the recent progress in research and development dealing with polymers derived from plant oils. It highlights the widening interest in novel approaches to the synthesis, characterization, and properties of these materials from renewable resources and emphasizes their growing impact on sustainable macromolecular science and technology. The monomers used include unmodified triglycerides, their fatty acids or the corresponding esters, and chemically modified triglycerides and fatty acid esters. Comonomers include styrene, divinylbenzene, acrylics, furan derivatives, epoxides, etc. The synthetic pathways adopted for the preparation of these materials are very varied, going from traditional free radical and cationic polymerizations to polycondensation reactions, as well as metatheses and Diels-Alder syntheses. In addition to this general appraisal, the specific topic of the use of tung oil as a source of original polymers, copolymers, and (nano)composites is discussed in greater detail in terms of mechanisms, structures, properties, and possible applications.

Investigating effects of high cellulase concentration on the enzymatic hydrolysis of the sisal cellulosic pulp.

The goal of this study was to investigate how the use of high concentration of cellulase may impact the properties of the substrate and the reaction medium during the enzymatic hydrolysis of the sisal pulp. Enzyme concentration of 0.9 mL g-1 was considered for hydrolysis of a sisal cellulosic substrate, and the results were compared with previous ones using 0.5 mL g-1 as cellulase concentration. Nonhydrolyzed pulps and the liquors were withdrawn from the reaction medium and characterized by scanning electron microscopy, crystallinity index, average molar mass, length/thickness, and high-performance liquid chromatography (HPLC). The results indicated that the enzyme/substrate ratio impacted crystallinity variations during the reaction and the induction period for exoglucanase action. The concentration of 0.9 mL g-1 led to a glucose yield (98%, an almost quantitative conversion) higher than 0.5 mL g-1 (89%). Aiming to gain information on the post-burst phase (after 15 h), 1 g of sisal pulp was added, and the results demonstrated that the enzymes remained active, which can counterbalance the higher cost due to the use of high enzymes concentrations. This study deepened the understanding of the enzymatic hydrolysis of sisal cellulosic pulp, and the findings may also benefit investigations on other pulps.