Enhanced ethanol production at commercial scale from molasses using high gravity technology by mutant S. cerevisiae

Abstract Very high gravity (VHG) technology was employed on industrial scale to produce ethanol from molasses (fermented) as well as by-products formation estimation. The effect of different Brix° (32, 36 and 40) air-flow rates (0.00, 0.20, 0.40, and 0.60 vvm) was studied on ethanol production. The maximum ethanol production was recorded to be 12.2% (v/v) at 40 Brix° with 0.2 vvm air-flow rate. At optimum level aeration and 40 Brix° VHG, the residual sugar level was recorded in the range of 12.5-18.5 g/L, whereas the viable cell count remained constant up to 50 h of fermentation and dry matter production increased with fermentation time. Both water and steam consumption reduced significantly under optimum conditions of Brix° and aeration rate with compromising the ethanol production. Results revealed VHG with continuous air flow is viable technique to reduce the ethanol production cost form molasses at commercial scale.

Performance and microbial community analysis of a full-scale hybrid anaerobic-aerobic membrane system for treating molasses-based bioethanol wastewater

We evaluated the efficacy of a full-scale combined biophysicochemical system for treating molasses-based bioethanol wastewater in terms of organic substances, nutrient, and dark brown color removal. The main organic removal unit, i.e., the upflow anaerobic sludge blanket [UASB] reactor, achieved 80.7% removal and 4.3 Nm3 methane production per cubic meter of wastewater with a hydraulic retention time of 16.7 h. Downflow hanging sponge [DHS] reactors were important in reducing the biochemical oxygen demand [BOD], and the lowest possible organic waste intake prevented excessive biomass formation. The BOD removal efficiency was 71.2-97.9%. The denitrification upflow anaerobic fixed bed [UFB] reactor achieved 99.2% total nitrogen removal. Post-physicochemical membrane treatment reduced the total phosphate, color, and remaining organic matter by 90.4%, 99.1%, and 99.8%, respectively. We analyzed the microbial diversity of the sludge from the UASB reactors. Methanosaeta was the dominant archaeal genus in the system, followed by Methanolinea, Methanomicrospillum, Caldiserica, Bacteroidetes, and Deltaproteobacteria

Análises microbiológicas do açúcar mascavo / Microbiolgical analyzes for brown sugar

Mascavo é um tipo de açúcar não refinado com um intenso sabor de melaço. Sua produção, praticamente artesanal, o torna, na maioria das vezes, susceptível as contaminações microbiológicas. Com o objetivo de se conhecer a qualidade microbiológica do açúcar mascavo comercializado, foram coletadas amostras de diferentes produtores que comercializam este tipo de açúcar no mercado. As avaliações foram realizadas com relação ao teor de umidade e a presença de bactérias mesófilas aeróbias totais, bactérias termófilas aeróbias produtoras de H2S (Desulfotomaculum nigrificans), bactérias termófilas anaeróbias não produtoras de H2S (Clostridiun thermosaccharolyticum), bactérias termófilas aeróbias totais e "flat sour", bolores e leveduras e coliformes totais e fecais. Os teores médios de umidade para as amostras de açúcar mascavo analisados variaram de 2,14 a 3,66 por cento, ou seja, de 7 a 11 vezes maior que as médias de umidade do açúcar cristal branco. Este fato explica o reduzido tempo para consumo deste produto. Pelas análises das amostras efetuadas nos últimos três anos observou-se que o açúcar mascavo produzido recentemente possui menor teor de umidade que em anos anteriores. Os resultados das análises microbiológicas mostraram que as marcas dos açúcares mascavos analisados estavam de acordo com os padrões oficiais de qualidade para bactérias termófilas anaeróbias produtoras de H2S (Desulfotomaculum nigrificans), Salmonella e bactérias do grupo coliformes. Entretanto, constataram-se contaminações a níveis críticos para bactérias mesófilas, bolores e leveduras, depreciando a qualidade do açúcar e comprometendo o tempo de armazenamento.

Brown Sugar is a type of unrefined sugar with a strong molasses flavour. Its production, is almost entirely handmade, and thus, susceptible to microbiological contamination. The aim of this research was to evaluate the brown sugar microbiological quality at different production regions, and commercialized at the supermarkets. Samples of crystal, refined and raw sugars were analyzed. The moisture, aerobic mesophile, thermophilic anaerobic, H2S aerobic thermophile (Desulfotomaculum nigrificans), H2S aerobic thermophile (acid nonproducing) (Clostridiun thermosaccharolyticum), flat sour, moulds, yeasts, Salmonella and coliforms were analyzed as well. The moisture of brown sugar ranged from 2.14 to 3.66 percent. These data are ten times the moisture level found for crystal sugar samples. Therefore, the shelf time for the brown sugar is reduced drastically. The microbiological analyzes showed the brown sugar samples meet the requirements established by the Comission on Microbiological Specification for Foods for H2S-producing aerobic thermophile (Desulfotomaculum nigrificans), Salmonella and coliforms. Contamination by mesophile bacteria, mould and yeast was critical for some samples, and therefore, decreases the quality of sugar and reduces storage time.

Growth of Pediococcus acidilactici on sugar cane blackstrap molasses

Pediococcus acidilactici (IL01) has grown in MRS (Man, Rogosa and Sharpe) broth modified by substitution of glucose by 2.0(per cent) (MRS-2), 3.0(per cent) (MRS-3), 4.0(per cent) (MRS-4) and 5.0 (per cent) (MRS-5) sugar cane blackstrap molasses. The highest acid production was obtained in MRS-5 broth maintained at a constant pH of 5.0. The higest biomass production was obtained when P. acilactici was grown in MRS-5 broth at initial pH6.5, while productivity was higher in MRS-2 broth (28.16per cent). When the MRS-2broth was utilized at initial pH 6.5 for a 20-hour fermentation period, the highest growth rate (dx/dt) was found in a period of 8 to 16 hours (0.290 g cells/L.h), while the specific growth rate (µ) was 0.175 (h-1) for that period, differently from the 0,441 (h-1) obtained for the period comprising the 4th to the 12th hour. The growth in MRS broth was 5.08(per cent) (2.95g/1) higher than in MRS-2 broth (2.80 g/1). The data obtained have shown that P. acidilactici has had a significant growth in molasses as the main carbon source, and that it is possible to substitute MRS glucose by this carbon source with the purpose of obtaining a more economical growth medium for the potential large scale productions.

Caracterizaçäo da microbiota bacteriana contaminante do caldo-de-cana durante a etapa de resfriamento em torre no processo de produçäo de álcool / Characterization of contaminant bacterial microbiota in sugar cane juice during the stage of cooling tower in alcohol production process

Amostras de caldo-de-cana clarificado a pasteurizado foram coletadas na entrada e saída de uma torre de resfriamento, no final da safra de cana de 1985. Contagem de microrganismos aeróbicos em placas evidenciou uma significativa variaçäo no número de contaminantes do caldo, durante a passagem pela torre, com elevaçäo (média logarítmica) de 10 vezes nas contagens em PCA e de 5,5 vezes nas contagens em MRS, acompanhadas de um decréscimo médio de 0,35 nos valores de pH das amostras. Dentre os tipos de bactérias presentes no caldo, a maior variaçäo observada foi na populaçäo de Leuconostoc, que apresentou uma elevaçäo de 46% da entrada para a saída da torre. A microbiota isolada mostrou-se predominantemente bacteriana (88%0 e Gram positiva (87%), sendo Lactobacillus o contaminante mais freqüente (38%), seguido de Staphylococcus (23%), Leuconostoc (12%), Bacillus (3%) Klebsiella (1%). As cepas de Lactobacillus foram classificadas como L. fermentus (33%), L. conbfusus (18%), L. viridescens (11%) e L. plantarum (2%). As demais ficaram com a identidade provável entre L. fermentus/L. reuteri (15%), L. brevis/L.buchneri (4%), L. fermentus/L.reuteri/L. buchneri (7%) e 10% näo foram identificadas. As cepas de Leuconostoc foram classificadas como L. mesenteroides subsp. mesenteroides (50%), L. paramesenteroide (27%) e L. mesenteroides subsp. dextranicum (23%)