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Sweet sorghum was investigated to an alternate feedstock for fuel ethanol production. juices from 4 sorghum varieties (BRS 506, BRS 508, BRS 509, BRS 511 and BRS); all developed by Embrapa (Brazilian Agricultural Research Corporation) Maize and Sorghum) were evaluated for sugar, starch and nutrient contents and theoretical ethanol yields. The levels of nitrogen, phosphorus, calcium, magnesium, starch and sugars (glucose, fructose and sucrose) were measured weekly over a period of 70 days. Fermentations were performed using yeast Saccharomyces cerevisiae. BRS 508, BRS 509 and BRS 511 showed potential to be useful for industrial applications for maturities exceeding 30 days. BRS 511 showed the highest sugar production, with levels higher than 140 g/L during the majority of the experiment and reaching a maximum of 191 g/L. All varieties showed similar behaviors with respect to nutrient content, which was characterized by a decrease in nutrient concentrations over the period analyzed. Juice from BRS 508 was successfully fermented within 8 h with a productivity (9.0 g/L h) and yield (90.5% of theoretical) similar to those observed for sugar cane juice.

Nowadays, hydrogen produced globally has been synthesized from fossil fuel with limited source. Therefore, research has been developed in order to explore biological H2 production by dark fermentation. The purpose of this work was to evaluate the effect of initial pH and ferrous sulfate and ammonium sulfate concentrations on the production of biohydrogen by dark fermentation. The process was carried out in batch mode under anaerobic conditions, in the absence of light, and at standard room temperature and pressure. A microbial consortium provided by the effluent treatment plant of a local dairy company was inoculated into a synthetic medium supplemented with cheese whey permeate (20 g/L of lactose) as a carbon source. The influence of three variables was analyzed by a central composite design 2((3)), and the optimum results of hydrogen yield (4.13 mol H2/mol lactose) and productivity (86.31 mmol H2/L/day) were achieved at initial pH 7.0 and FeSO4 and (NH4)2SO4 concentrations of 0.6 and 1.5 g/L, respectively. Under these conditions, the kinetic parameters of fermentation were investigated by analyzing the profile of H2 yield and productivity, metabolite concentrations, pH, and concentration of dissolved iron. In the kinetic analysis, the modified Gompertz equation described adequately the fermentative hydrogen production from cheese whey permeate (R (2) = 0.98). The profile of ethanol and volatile organic acids showed that lactic acid and butyric acid were the main metabolites produced, and the sum of both by-products corresponded to about 58 % of the total metabolites.

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The aim of this work was to produce ethanol using the acid hydrolysis of soybean molasses followed by alcoholic fermentation via submerged Saccharomyces cerevisiae. The influence of the acid type, pH, and absolute pressure of the hydrolysis on the ethanol yield and the total residual sugar concentration was evaluated using a factorial design (FD). The absolute pressure ranged from 1 to 2 atm; the pH ranged from 3 to 5; and three different acids were studied in the hydrolysis process: sulfuric, hydrochloric, and nitric acids. The experiments were conducted in an Applicon batch reactor with a useful volume of 1.5 L at a stirring speed of 230 rpm and with an inoculum concentration of 30 g/L. The inoculum volume used was 30% of the total volume. The best results, as determined by FD, were obtained at pH 4 and an absolute pressure of 1.5 atm for all of the acids studied. The highest ethanol yield was 46% for sulfuric acid, 48% for hydrochloric acid, and 54% for nitric acid. After the concentration of inoculum and the fermentation kinetics profiles were investigated, a 62% yield relative to the initial sugar content was obtained under optimum conditions after 14 h of fermentation and an inoculum concentration of 35 g/L.

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