The degradation of lactic acid under anoxic conditions was studied in several strains of Lactobacillus buchneri and in close relatives such as Lactobacillus parabuchneri, Lactobacillus kefir, and Lactobacillus hilgardii. Of these lactobacilli, L. buchneri and L. parabuchneri were able to degrade lactic acid under anoxic conditions, without requiring an external electron acceptor. Each mole of lactic acid was converted into approximately 0.5 mol of acetic acid, 0.5 mol of 1,2-propanediol, and traces of ethanol. Based on stoichiometry studies and the high levels of NAD-linked 1,2-propanediol-dependent oxidoreductase (530 to 790 nmol min−1 mg of protein−1), a novel pathway for anaerobic lactic acid degradation is proposed. The anaerobic degradation of lactic acid by L. buchneri does not support cell growth and is pH dependent. Acidic conditions are needed to induce the lactic-acid-degrading capacity of the cells and to maintain the lactic-acid-degrading activity. At a pH above 5.8 hardly any lactic acid degradation was observed. The exact function of anaerobic lactic acid degradation by L. buchneri is not certain, but some results indicate that it plays a role in maintaining cell viability.
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This letter to the editor argues that the assumption of a single value for the acetate recovery factor in carbon-13 stable isotope research for different individuals, can lead to significant errors in the outcomes of substrate utilization measurements.
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For children it is important to consume enough vegetables to establish healthy dietary patterns. Taste acceptance is an important factor contributing to food choice and consumption. Sweetness and sourness enhancement can increase acceptance of specific foods in children. The aim of this study was to determine the effect of sweetness and sourness enhancement on acceptance of cucumber and green capsicum purees in 5-6-year-old children. Three concentrations of sucrose (2, 5 and 10%) and citric acid (0.05, 0.08 and 0.15%) were added to cucumber and green capsicum purees. Children (n = 70, 5.7 ± 0.5 yrs) assessed acceptance of the vegetable purees using a 5-point hedonic facial scale. Sweetness enhancement significantly increased acceptance of cucumber purees (5 and 10% sucrose) and green capsicum purees (2 and 10% sucrose) compared to unmodified purees. Sourness enhancement (0.05, 0.08 and 0.15% citric acid) did not significantly influence acceptance of cucumber and green capsicum purees compared to unmodified purees. Children differed in acceptance of vegetable purees with added sucrose and citric acid. Sweetness likers (cucumber 77.1%, green capsicum 58.6%) accepted sucrose concentrations better than sweetness non-likers in both vegetables. Sourness likers (cucumber 50.0%, green capsicum 44.3%) accepted medium and high concentrations of citric acid better than sourness non-likers in cucumber and all citric acid concentrations in green capsicum. We conclude that enhancement of sweetness increases acceptance of cucumber and green capsicum purees in most children whereas enhancement of sourness is better accepted by only a few children. This study highlights the challenge to get children to better accept vegetables, since only sweetness enhancement improved acceptance while addition of sucrose is undesirable. For a small subset of children enhancing sourness might be an alternative strategy to increase acceptance of vegetables
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Carboxylated cellulose is an important product on the market, and one of the most well-known examples is carboxymethylcellulose (CMC). However, CMC is prepared by modification of cellulose with the extremely hazardous compound monochloracetic acid. In this project, we want to make a carboxylated cellulose that is a functional equivalent for CMC using a greener process with renewable raw materials derived from levulinic acid. Processes to achieve cellulose with a low and a high carboxylation degree will be designed.
