Gene regulation of the Lactobacillus vini in response to industrial stress in the fuel ethanol production.

The industrial ethanol fermentation imposes several stresses to microorganisms. However, some bacterial species are well adapted and manage to endure these harmful conditions. Lactobacillus vini is one of the most found bacteria in these environments, indicating the existence of efficient tolerance mechanisms. In view of this premise, the present study aimed to describe the tolerance of L. vini to several stressing agents encounter in industrial environments and the genetic components of the stress response. In general, L. vini showed significant tolerance to stressors commonly found in fuel-ethanol fermentations, and only doses higher than normally reached in processes restrained its growth. The lag phase and the growth rate were the most responsive kinetic parameter affected. Gene expression analysis revealed that uspII gene positively responded to all conditions tested, a typical profile of a general stress response gene. In addition, the results also revealed aspects of regulatory modules of co-expressed genes responding to different stresses, and also the similarities of response mechanism with basis in common cellular damages. Altogether, these data contribute to uncover the factors that could favour L. vini in the industrial fermentation which could be shared with other well adapted species and reports the first stress response genes in this bacterium.

Nutritional requirements for Lactobacillus vini growth in sugarcane derivative substrate of ethanol fermentation.

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.

Lactobacillus vini: mechanistic response to stress by medium acidification.

This work describes the response of Lactobacillusvini, a bacterium found as a contaminant in winemaking and fuel ethanol fermentation processes, to acid stress caused by inorganic or weak organic acids. First, we observed for the first time that bacterial cells become resistant to lysis by lysozyme when submitted to acidic stress. Then, the predicted intracellular acidification can be reversed by the presence of arginine, histidine and glutamine. However, these molecules were not able to reverse the effect of resistance to lysis, indicating the independence of these mechanisms. In general, a reduction in the expression of the main genes involved in the synthesis and deposition of material in the cell wall was observed, whereas the genes involved in the reabsorption of this structure showed increased expression. These data suggested that L. vini responds to the acidification of the medium through early entry into the stationary phase, firing two signals for cell wall remodelling and maintenance of intracellular pHin a coordinated way, most probably by alkalization and the proton extrusion process. If this picture is conserved among lactobacilli, it may not only have an impact on research associated with fermentation processes, but also on that associated with probiotic improvement.

Cyanobacteria community in two tropical eutrophic reservoirs in northeastern Brazil / Comunidade de cianobactérias em dois reservatórios eutróficos e tropicais no nordeste do Brasil

This study investigated the effect of seasonality on the Cyanobacteria community in two tropical eutrophic reservoirs in northeastern Brazil. Monthly samplings were conducted in the sub-surface of reservoirs. The following abiotic variables were analyzed: apparent color, turbidity, conductivity, alkalinity, calcium, magnesium, sodium, potassium, sulfate, total phosphorous, ammonia, nitrate, nitrite, chlorides, total hardness and chlorophyll-a, according to APHA (2012). Cyanobacteria density was quantified through biomass. Data were analyzed using one-way ANOVA and Redundancy Analysis (RDA). Higher mean values of Cyanobacteria biomass occurred in the dry (9.9mm3 L-1) and rainy (19.0mm3 L-1) season in Jucazinho and Carpina reservoirs, respectively, especially Planktothrix agardhii, Cylindrospermopsis raciborskii and Geiterinema amphibium, which occurred in 100% of the samples. RDA analysis revealed that the variables nitrite, ammonia, conductivity, calcium, sulfate, chlorides and alkalinity influenced most the Cyanobacteria community in both reservoirs. High trophic state index was observed throughout the year. Seasonality affected both biotic and abiotic variables.

Este estudo investigou o efeito da sazonalidade sobre a comunidade de cianobactérias em dois reservatórios eutróficos tropicais no nordeste do Brasil. Mensalmente, amostras foram coletadas na subsuperfície dos reservatórios. Foram analisados os seguintes fatores abióticos: cor aparente, turbidez, condutividade, alcalinidade, cálcio, magnésio, sódio, potássio, sulfato, fósforo total, amônia, nitrato, nitrito, cloretos, dureza total e clorofila-a, de acordo com APHA (2012). A densidade de cianobactérias foi quantificada por meio de sua biomassa. Os dados foram analisados usando Anova (one-way) e Análise de Redundância (RDA). Maiores valores médios de biomassa de cianobactérias ocorreram na estação seca (9,9 mm3 L-1) e chuvosa (19,0 mm3 L-1) nos reservatórios de Jucazinho e Carpina, respectivamente, especialmente Planktothrix agardhii, Cylindrospermopsis raciborskii e Geitlerinema amphibium que ocorreram em 100% das amostras. A análise de RDA revelou que os parâmetros nitrito, amônia, condutividade, cálcio, sulfato, cloretos e alcalinidade foram mais influentes na comunidade de Cyanobacteria em ambos os reservatórios. Elevado índice de estado trófico foi detectado durante todo o ano. A sazonalidade exerceu influência tanto nas variáveis bióticas como abióticas.