Hydrothermal pretreatment for the production of prebiotic oligosaccharides from tobacco stem.

Tobacco stem is an abundant and inexpensive renewable source to produce prebiotics by circular economy. In this study, hydrothermal pretreatments were evaluated on the release of xylooligosaccharides (XOS) and cello-oligosaccharides (COS) from the tobacco stem by a central composite rotational design associated with response surface methodology to evaluate the effects of temperature (161.72 to 218.

An overview on fermentation strategies to overcome lignocellulosic inhibitors in second-generation ethanol production using cell immobilization.

The development of technologies to ferment carbohydrates (mainly glucose and xylose) obtained from the hydrolysis of lignocellulosic biomass for the production of second-generation ethanol (2G ethanol) has many economic and environmental advantages. The pretreatment step of this biomass is industrially performed mainly by steam explosion with diluted sulfuric acid and generates hydrolysates that contain inhibitory compounds for the metabolism of microorganisms, harming the next step of ethanol production. The main inhibitors are: organic acids, furan, and phenolics.

Redox potential as a key parameter for monitoring and optimization of xylose fermentation with yeast Spathaspora passalidarum under limited-oxygen conditions.

The determination of optimum values of volumetric oxygen transfer coefficient (ka) for Spathaspora passalidarum is an important aspect for the optimization of ethanol production from pentoses since oxygen plays a key role on yeast metabolism. By studying the fermentation of a xylose and glucose mixture, the highest ethanol volumetric productivity was achieved at a ka of 45 h (1.12 g L h), reducing the fermentation time to half when compared to other oxygen-limiting conditions that were considered optimum for other native strains, besides increasing xylose consumption rates.

Online monitoring of the redox potential in microaerobic and anaerobic Scheffersomyces stipitis fermentations.

Objective: A correlation among different volumetric oxygen transfer coefficients (ka) and the oxireduction potential (ORP) in batch fermentations using Scheffersomyces stipitis was evaluated. Experiments were performed using a mixture of xylose and glucose as the substrates.

Results: Microaerophilic condition (ka = 4.

Cachaça yeast strains: alternative starters to produce beer and bioethanol.

This work was performed to verify the potential of yeast strains isolated from cachaça distilleries for two specific biotechnological applications: beer and bioethanol production. In the beer production, the strains were tested for characteristics required in brewery practices, such as: capacity to ferment maltose and maltotriose, ability to grow at lowest temperatures, low HS production, and flocculation profile. Among the strains tested, two of them showed appropriate characteristics to produce two different beer styles: lager and ale.

Fermentation strategy for second generation ethanol production from sugarcane bagasse hydrolyzate by Spathaspora passalidarum and Scheffersomyces stipitis.

Alcoholic fermentation of released sugars in pretreatment and enzymatic hydrolysis of biomass is a central feature for second generation ethanol (E2G) production. Saccharomyces cerevisiae used industrially in the production of first generation ethanol (E1G) convert sucrose, fructose, and glucose into ethanol. However, these yeasts have no ability to ferment pentose (xylose).