ABSTRACT Microbial contamination of the wort during the fermentation process causes significant losses in ethanol production worldwide and creates a dependence of the industry on chemicals and antibiotics to control contamination. Therefore, this study used electron beam (e-beam) to disinfect wort from sugarcane (Saccharum officinarum L.) molasses and investigate the bioethanol fermentation. Four treatments (T0 – T3) were carried out using ionizing doses of radiation through the electron accelerator: 0 (control), 10, 20, and 40 kGy. Total mesophiles, total bacteria, sucrose, glucose, fructose, phenolics, flavonoids, hydroxymethylfurfural (5-HMF), and Furfural were measured. An alcoholic fermentation assay was performed after the irradiation process. The irradiated treatments showed no inversion of sugars and formation of the inhibitory by-products flavonoids, furfural and 5-HMF, except for the phenolic compounds. The lower dose tested (10 kGy) reduced more than 99.9 % of the total mesophiles and more than 99.99 % of the total bacteria in the substrate. In the fermentation, the irradiated worts presented similar (p > 0.05) yields (92, 93, and 94 %) and ethanol productivity levels (0.89, 0.88, and 0.87 g L–1 h–1, for T1, T2, and T3 respectively). However, all treatments presented higher yields and productivity (p < 0.05) when compared to the control (88 % and 0.85 g L–1 h–1), highlighting the possible use of e-beam in wort fermentation at a lower dose (10 kGy). This allows reduction in losses caused by microbial contamination, besides increasing fermentation yield and productivity with lower energy consumption.

Abstract The Very High Gravity (VHG) fermentation is a technology that can lead to a reduction in waste generation, a reduction in energy consumption and GHG emissions and several technical, economic, and environmental advantages. Having, as a limiting factor, yeast tolerance to the most diverse stressors in the fermentation medium. To overcome this limitation, the aim of the work was to verify the potential protective effect of silica (+A) on Saccharomyces cerevisiae (Ethanol Red®) submitted to VHG fermentation. Initially, an adaptive test to VHG fermentation was carried out, with 5 cell recycles in musts from sugar cane syrup. Each recycle was subjected to the treatments, in quadruplicate: T1C (control) - Wort without silica supplementation; T2S100- Wort with supplementation of 100 mg L-1 of silica and T3S300- Wort with supplementation of 300 mg L -1 of silica. As a result, the T3S300 treatment in the adaptive test, showed viability of 77.5 to 81.55%; biomass production from 8.1 to 10.0 g L-1; yield from 90.0 to 95.3% and productivity from 7.3 to 10.9 mL L-1h-1. In conclusion, the treatment of the wort with silica (+A) (100 and 300 mg L-1) has an effect protector on yeast and may present positive responses in VHG fermentations.

O comportamento da viabilidade celular de leveduras é essencial quando se almeja utilizá-la como um probiótico e o veículo que assegure esta propriedade até o momento do consumo é particularmente. Sobre grãos de milho, contendo 16 ou 20% de umidade, foram aplicadas leveduras desidratadas vivas, nas concentrações de 1 e de 2%. A viabilidade celular foi avaliada nos períodos de 0, 15, 30, 90 e 110 dias de armazenamento. A viabilidade celular nas leveduras não diferiu estatisticamente entre os tratamentos aos 30 dias em armazenamento, com a viabilidade média de 89,10%. A viabilidade média encontrada aos 90 dias de 72,20% foi menor do que aquelas nos três primeiros períodos de armazenamento. Após 110 dias de armazenamento foi de 61,14%. Conclue-se que leveduras apresentam viabilidade celular até 110 dias em armazenamento sobre milho e que estes podem ser utilizados como um veículo para a aplicação da levedura como um probiótico.

Yeasts were applied to corn grains, containing 16 or 20% moisture, at concentrations of 1 and 2%. The cellular viability was assayed at 0, 15, 30, 90 and 110 days. The cellular viability did not differ statistically among the treatments up to 30 days of storage, with the median viability of 89.10%. The average viability found at 90 days (72.20%) was lower than in the first three storage periods. After 110 days, the average viability was 61.14%. In conclusion, since yeast cells were viable up to 110 days in storage on corn grains, these can be used as a vehicle for the application of yeast as a probiotic.

As aflatoxinas são metabólitos hepatotóxicos produzidos por algumas linhagens de Aspergillus flavus, A. parasiticus e, eventualmente, por A. nomius sobre grande número de produtos agrícolas. Esta pesquisa foi conduzida para avaliar a capacidade de Saccharomyces cerevisiae, nas formas termolisada e desidratada viva, em reduzir os danos causados por aflatoxinas. Para tal, foi preparada uma dieta básica e desta se obtiveram quatro formulações: uma como controle; as demais contaminadas com aflatoxinas na concentração de 400 mig kg-1, sendo duas com posterior adição de 1% de leveduras, uma na forma termolisada e outra como desidratada viva. Um bioensaio com duração de 28 dias foi efetuado com ratos Wistar. Foram realizados os estudos do peso relativo de órgãos internos e a análise do tecido hepático dos animais. Os pesos relativos de órgãos internos de animais submetidos aos diferentes tratamentos não diferiram estatísticamente entre si; o tecido do fígado dos animais submetidos à dieta livre de aflatoxinas foi adotado como padrão de isento de toxidez; o tecido hepático dos animais que receberam dieta controle com aflatoxinas apresentaram sinais claros de toxicidade; os animais que receberam dieta com aflatoxinas + 1% de levedura termolisada apresentaram sinais de toxicidade semelhantes ao controle com aflatoxinas; o tecido hepático dos animais que receberam dieta com aflatoxinas + 1% de levedura viva apresentaram sinais de toxicidade menores do que os animais que receberam a dieta controle com aflatoxinas. As leveduras termolisadas não foram capazes de suprimir os efeitos das aflatoxinas; as leveduras vivas apresentaram habilidade de reduzir os efeitos promovidos por aflatoxinas.

Aflatoxins are hepatotoxic metabolites produced by Aspergillus flavus and A. parasiticus on a number of agricultural commodities. This research was carried out to evaluate the ability of thermolysed and active Saccharomyces cerevisiae to attenuate liver damage caused by aflatoxin. Diets were prepared containing 0 aflatoxin; 400 mug kg-1 aflatoxin; 400 mug kg-1 aflatoxin plus 1% of dehydrated active yeast, and 400 mug kg-1 aflatoxin plus 1% of thermolysed yeast. A bioassay with Wistar rats was conducted for 28 days, and body organs were weighted and analyses of the liver tissue of the animals were performed. The relative weight of heart, kidneys and liver from animals submitted to the different treatments did not show any difference, and liver tissue of animals feeding on the aflatoxin-free diet was adopted as a toxicity-free pattern. Hepatic tissue of animals feeding on diets containing 400 mug kg-1 aflatoxin or the diet supplemented with 1% thermolysed yeast showed clear signs of toxicity and damage. Hepatic tissue of animals feeding on the diet containing 1% of dehydrated active yeast showed less toxicity signs and damage than those receiving the diet containing 400 mug kg-1 aflatoxin. Active, dehydrated yeast had the ability to reduce toxic effects caused by aflatoxin, but thermolysed yeast was not able to alleviate the effects of aflatoxin toxicity.