Engineering cellular redox homeostasis to optimize ethanol production in xylose-fermenting Saccharomyces cerevisiae strains.

The transition from fossil fuels dependency to embracing renewable alternatives is pivotal for mitigating greenhouse gas emissions, with biorefineries playing a central role at the forefront of this transition. As a sustainable alternative, lignocellulosic feedstocks hold great promise for biofuels and biochemicals production. However, the effective utilization of complex sugars, such as xylose, remains a significant hurdle.

Modeling the influence of propionic acid concentration and pH on the kinetics of Salmonella Typhimurium.

Salmonella Typhimurium is a foodborne pathogen often found in the poultry production chain. Antibiotics have been used to reduce S. Typhimurium contamination in poultry aviaries and improve chicken growth.

First- and second-generation integrated process for bioethanol production: Fermentation of molasses diluted with hemicellulose hydrolysate by recombinant Saccharomyces cerevisiae.

The integration of first- (1G) and second-generation (2G) ethanol production by adding sugarcane juice or molasses to lignocellulosic hydrolysates offers the possibility to overcome the problem of inhibitors (acetic acid, furfural, hydroxymethylfurfural and phenolic compounds), and add nutrients (such as salts, sugars and nitrogen sources) to the fermentation medium, allowing the production of higher ethanol titers. In this work, an 1G2G production process was developed with hemicellulosic hydrolysate (HH) from a diluted sulfuric acid pretreatment of sugarcane bagasse and sugarcane molasses. The industrial Saccharomyces cerevisiae CAT-1 was genetically modified for xylose consumption and used for co-fermentation of sucrose, fructose, glucose, and xylose.

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.

Potential of Mortierellaceae for polyunsaturated fatty acids production: mini review.

The health benefits of polyunsaturated fatty acids (PUFAs) have encouraged the search for rich sources of these compounds. However, the supply chain of PUFAs from animals and plants presents environmental concerns, such as water pollution, deforestation, animal exploitation and interference in the trophic chain. In this way, a viable alternative has been found in microbial sources, mainly in single cell oil (SCO) production by yeast and filamentous fungi.

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.

Fermentation strategies to improve propionic acid production with ssp.: a review.

Propionic acid (PA) is a carboxylic acid applied in a variety of processes, such as food and feed preservative, and as a chemical intermediate in the production of polymers, pesticides and drugs. PA production is predominantly performed by petrochemical routes, but environmental issues are making it necessary to use sustainable processes based on renewable materials. PA production by fermentation with the genus is a promising option in this scenario, due to the ability of this genus to consume a variety of renewable carbon sources with higher productivity than other native microorganisms.

Comparison of Spathaspora passalidarum and recombinant Saccharomyces cerevisiae for integration of first- and second-generation ethanol production.

First-generation ethanol (E1G) is based on the fermentation of sugars released from saccharine or starch sources, while second-generation ethanol (E2G) is focused on the fermentation of sugars released from lignocellulosic feedstocks. During the fractionation process to release sugars from hemicelluloses (mainly xylose), some inhibitor compounds are released hindering fermentation. Thus, the biggest challenge of using hemicellulosic hydrolysate is selecting strains and processes able to efficiently ferment xylose and tolerate inhibitors.

Secretome analysis as a tool to elucidate bacterial contamination influence during second-generation ethanol production in a Melle-Boinot process.

Melle-boinot fermentation process can be used to increase the ethanol productivity in second-generation ethanol process (2G). However, bacterial contamination can result in decreased ethanol production and sugars consumption. The available literature on microbial contamination in the 2G at the secretome level, microbial interactions and their impacts on ethanol production are scarce.

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.

Effect of contamination with Lactobacillus fermentum I2 on ethanol production by Spathaspora passalidarum.

Second-generation bioethanol is a promising source of renewable energy. In Brazilian mills, the production of ethanol from sugarcane (first generation, 1G) is a consolidated process performed by Saccharomyces cerevisiae and characterized by high substrate concentrations, high cell density, and cell recycle. The main bacterial contaminants in 1G fermentation tanks are lactic acid bacteria, especially bacteria from the Lactobacillus genus, which is associated with a decrease in ethanol yield and yeast cell viability, among other negative effects.

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.

Sugarcane must fed-batch fermentation by Saccharomyces cerevisiae: impact of sterilized and non-sterilized sugarcane must.

The presence of microbial contaminants is common in the sugarcane ethanol industry and can decrease process yield, reduce yeast cell viability and induce yeast cell flocculation. To evaluate the effect of microbial contamination on the fermentation process, we compared the use of sterilized and non-sterilized sugarcane must in the performance of Saccharomyces cerevisiae with similar fermentation conditions to those used in Brazilian mills. Non-sterilized sugarcane must had values of 10 and 10 CFU mL of wild yeast and bacterial contamination, respectively; decreased total reducing sugar (TRS); and increased lactic and acetic acids, glycerol and ethanol concentrations during storage.

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).

The aldo-keto reductase: a multipurpose enzyme for biorefinery applications.

Background: In nature, termites can be considered as a model biological system for biofuel research based on their remarkable efficiency for lignocellulosic biomass conversion. Redox enzymes are of interest in second-generation ethanol production because they promote synergic enzymatic activity with classical hydrolases for lignocellulose saccharification and inactivate fermentation inhibitory compounds produced after lignocellulose pretreatment steps.

Results: In the present study, the biochemical and structural characteristics of the aldo-keto reductase (AKR-1) were comprehensively investigated.

Bioethanol production by recycled Scheffersomyces stipitis in sequential batch fermentations with high cell density using xylose and glucose mixture.

Here, it is shown three-step investigative procedures aiming to improve pentose-rich fermentations performance, involving a simple system for elevated mass production by Scheffersomyces stipitis (I), cellular recycle batch fermentations (CRBFs) at high cell density using two temperature strategies (fixed at 30°C; decreasing from 30 to 26°C) (II), and a short-term adaptation action seeking to acclimatize the microorganism in xylose rich-media (III). Cellular propagation provided 0.52gdrycellweightgRS(-1), resulting in an expressive value of 45.

Poly(3-Hydroxybutyrate) Production in Repeated fed-Batch with Cell Recycle Using a Medium with low Carbon Source Concentration.

Among approaches applied to obtain high productivity and low production costs in bioprocesses are high cell density and the use of low cost substrates. Usually low cost substrates, as waste/agroindustrial residues, have low carbon concentration, which leads to a difficulty in operating bioprocesses. Real time control of process for intracellular products is also difficult.

High-cell-density culture strategies for polyhydroxyalkanoate production: a review.

This article gives an overview of high-cell-density cultures for polyhydroxyalkanoate (PHA) production and their modes of operation for increasing productivity. High cell densities are very important in PHA production mainly because this polymer is an intracellular product accumulated in various microorganisms, so a high cellular content is needed for the polymer production. This review describes relevant results from fed-batch, repeated batch, and continuous modes of operation without and with cell recycle for the production of these polymers by microorganisms.

Carbon source pulsed feeding to attain high yield and high productivity in poly(3-hydroxybutyrate) (PHB) production from soybean oil using Cupriavidus necator.

Poly(3-hydroxybutyrate) (PHB) biosynthesis from soybean oil by Cupriavidus necator was studied using a bench scale bioreactor. The highest cell concentration (83 g l(-1)) was achieved using soybean oil at 40 g l(-1) and a pulse of the same concentration. The PHB content was 81% (w/w), PHB productivity was 2.