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Lactobacillus vini is a bacterial contaminant found in industrial environments of winemaking and fuel-ethanol fermentation. However, there has been no standard analysis of its physiology that can pinpoint its adaptive traits to these kinds of environments. In view of this lack of information, the aim of this study is to determine the nutritional factors that lead to the growth of L. vini in the industrial plants of fuel-ethanol. First of all, the limited growth of this bacterium was studied in the industrial substrate, which was improved by nutritional supplementation with amino acids, and its homofermentative status was confirmed. Metabolite analysis showed that citrate is a growth factor of paramount importance for this bacterium in industrial processes through pyruvate metabolization, and increases ATP production and biomass formation. Furthermore,e acetate uptake, either from the medium or generated from citrate metabolism, was assimilated for biomass production. Hence, a metabolic model was designed to describe the role of citrate and acetate in the growth of L. vini that could be tested on other lactobacilli., (© FEMS 2019.)

Large amounts of residues generated by agricultural, urban and industrial activities are dumped daily on the soil. This practice deserves special attention because it causes serious environmental problems. This study evaluated the toxic potential of the sugarcane vinasse, a by-product of the sugar-alcohol industry, and the biosolid, a residue produced by wastewater treatment plants, both widely used as fertilizers. The evaluation was performed through bioassays using a typical soil bioindicator, the diplopod Rhinocricus padbergi. The specimens were exposed to soils containing these residues in concentrations that are compatible with the Brazilian regulation for agricultural use. Semi-quantitative immunolabelling analyses of the stress protein HSP70 were performed on the midgut of the studied diplopods. There was a significant increase in the immunolabelling of HSP70 proteins as a response to xenobiotics from both residues, particularly in regions where the function of the cells is the detoxification of the organ (e.g. the hepatic cell layer and specific regions of the epithelium). Higher immunolabelling was observed in the specimens exposed to vinasse in comparison with the biosolid exposure. This demonstrates that the substances in the tested residues had proteotoxic action in the exposed animals and induced a cytoprotective response, which led to higher stress protein immunolabelling. Therefore, caution is needed for the use of such residues in agriculture.

Although there are already commercial-scale productions of second generation (2G) ethanol, focusing efforts on process optimization can be of key importance to make the production cost-effective in large scale. In this scenario, mathematical models may be useful in design, scale-up, optimization, and control of bioreactors. For this reason, the aim of this work was to study the kinetics of the enzymatic hydrolysis of cellulose from sugarcane straw. Experiments using hydrothermally pretreated sugarcane (HPS) straw (195 °C, 10 min, 200 rpm) with and without alkaline delignification (4 % NaOH m/v, 30 min, 121 °C) were carried out in shake flasks (50 °C, pH 5.0, 200 rpm). Solid load was varied in a range of 0.8 to 10 % (m/v), in initial velocity and long-term assays. Enzyme concentration (Cellic®CTec2) was varied from 5 to 80 filter paper unit (FPU) gcellulose (-1). It was possible to fit Michaelis-Menten (MM), modified MM, with and without competitive inhibition by glucose, and Chrastil models. Chrastil model and modified MM with inhibition (both suitable for heterogeneous system, with high resistance to internal diffusion) showed more appropriate than pseudo-homogeneous MM model. The fitted models were able to identify key features of the hydrolysis process and can be very useful within the perspective of bioreactors engineering.

In the present work, we evaluated the mineral composition of three sugarcane varieties from different areas in northeast Brazil and their influence on the fermentation performance of Saccharomyces cerevisiae. The mineral composition was homogeneous in the different areas investigated. However, large variation coefficients were observed for concentrations of copper, magnesium, zinc and phosphorus. Regarding the fermentation performances, the sugarcane juices with the highest magnesium concentration showed the highest ethanol yield. Synthetic media supplemented with magnesium also showed the highest yield (0.45 g g(-1)) while the excess of copper led to the lowest yield (0.35 g g(-1)). According to our results, the magnesium is the principal responsible for the increase on the ethanol yield, and it also seems to be able to disguise the inhibitory effects of the toxic minerals present in the sugarcane juice.

This work describes the effects of the presence of the yeast Dekkera bruxellensis and the bacterium Lactobacillus vini on the industrial production of ethanol from sugarcane fermentation. Both contaminants were quantified in industrial samples, and their presence was correlated to a decrease in ethanol concentration and accumulation of sugar. Then, laboratory mixed-cell fermentations were carried out to evaluate the effects of these presumed contaminants on the viability of Saccharomyces cerevisiae and the overall ethanol yield. The results showed that high residual sugar seemed the most significant factor arising from the presence of D. bruxellensis in the industrial process when compared to pure S. cerevisiae cultures. Moreover, when L. vini was added to S. cerevisiae cultures it did not appear to affect the yeast cells by any kind of antagonistic effect under stable fermentations. In addition, when L. vini was added to D. bruxellensis cultures, it showed signs of being able to stimulate the fermentative activity of the yeast cells in a way that led to an increase in the ethanol yield.