RESUMO
Fermentations with three different xylose-utilizing recombinant Saccharomyces cerevisiae strains (F12, CR4, and CB4) were performed using two different wheat hemicellulose substrates, unfermented starch free fibers, and an industrial ethanol fermentation residue, vinasse. With CR4 and F12, the maximum ethanol concentrations obtained were 4.3 and 4 g/L, respectively, but F12 converted xylose 15% faster than CR4 during the first 24 h. The comparison of separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) with F12 showed that the highest, maximum ethanol concentrations were obtained with SSF In general, the volumetric ethanol productivity was initially, highest in the SHF, but the overall volumetric ethanol productivity ended up being maximal in the SSF, at 0.013 and 0.010 g/Lh, with starch free fibers and vinasse, respectively.
Assuntos
Catalase/metabolismo , Etanol/metabolismo , Polissacarídeos/metabolismo , Saccharomyces cerevisiae/metabolismo , Triticum/química , Triticum/microbiologia , Xilose/metabolismo , Catalase/química , Catalase/genética , Técnicas de Cocultura , Fontes Geradoras de Energia , Fermentação , Hidrólise , Resíduos Industriais/prevenção & controle , Polissacarídeos/química , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/classificação , Saccharomyces cerevisiae/genética , Especificidade da Espécie , Xilose/químicaRESUMO
Herd health and production records of 1161 Holstein-Friesian heifers from 22 Michigan dairy herds were utilized to study the effect of age at first calving upon reproductive efficiency, milk production and the incidence of disease in the first lactation. Age at first calving was not significantly related to either milk production or reproductive efficiency. Heifers displaying dystocia were significantly older at calving than those that calved without problems. Additionally, the incidence of ketosis was associated with a significantly greater age at first calving. Heifers with diarrhea and those that aborted were significantly younger at calving than their herdmates. Incidence of 12 other common dairy diseases was not related to age at first calving. It would, therefore, appear that the dairy producers we studied could inseminate their heifers at an earlier age, and thereby increase production per day of life, without suffering serious detrimental effects in lactational milk production, reproductive efficiency or overall disease incidence.
