Xylose and Arabinose Fermentation to Produce Ethanol by Isolated Yeasts from Durian (Durio zibethinus L.) Fruit

Xylose and arabinose are pentosesugars that present in hemicellulose, part of lignocellulose biomass.These pentose sugars can be fermented by yeast into ethanol.The aim of this research was to utilize yeast isolated from durian fruit (DuriozibethinusL.) in fermentation of xylose and arabinose to produce bioethanol.Phenotypic test of isolates was conducted by growingthe isolates in various agar media, i.e.YPD (Yeast Peptone Dextrose), YPA (Yeast Peptone Arabinose), and YPX (Yeast Peptone Xylose) containing dextrose, arabinose, xylose, respectively, assole carbon source to see cell growth. The yeast isolates were further identified using API AOC 20C kit method. Yeast isolates were applied for fermentation of glucose, arabinose, and xylosein incubated cultures. Ethanol production in the fermentation was analyzed bygaschromatography. Yeast isolates were identified as Kodamaea ohmeri, Candida famata, Candida guilliermondii, and Crytococcuc laurentii. Based on gas chromatography data, it was found that ethanol produced in the fermentation for three days, the highest ethanol content on xylose substrate was fermented by Candida famata-Awhich is0.021% (v/v) ethanol resulted from initial concentration of 5% xylose (w/v). While on arabinose substrate, the highest ethanol content was fermented by Crytococcus laurentii-Bwhich is 0.0034% (v/v) ethanol resulted from initial concentration of 5% arabinose (w/v).

Improvement of L-Arabinose Fermentation by Modifying the Metabolic Pathway and Transport inSaccharomyces cerevisiae

The L-arabinose utilization pathway was established inSaccharomyces cerevisiae, by expressing the codon-optimizedaraA,araB, andaraDgenes ofLactobacillus plantarum. After overexpressing theTAL1,TKL1,RPE1,RKI1, andGAL2genes and adaptive evolution, the L-arabinose utilization of the recombinant strain became efficient. The resulting strain displayed a maximum specific growth rate of 0.075 h−1, a maximum specific L-arabinose consumption rate of 0.61 g h−1 g−1dry cell weight, and a promising ethanol yield of 0.43 g g−1from L-arabinose fermentation.

The emerging strains of Shigella dysenteriae type 2 in Bangladesh are clonal

A total of 113 strains of Shigella dysenteriae type 2 isolated from patients attending the Dhaka diarrhoea treatment centre of ICDDR,B: Centre for Health and Population Research during the period 1999–2004 were studied. Serotype of the isolates was confirmed using commercially available antisera. Except for arabinose fermentation, all the strains had similar biochemical reactions. More than 60% of the strains were sensitive to commonly used antibiotics; only 6% (n=7) of the strains were resistant to nalidixic acid, and none of the strains were resistant to mecillinam and ciprofloxacin. All strains were invasive as demonstrated by the presence of a 140 MDa plasmid, ial, sen and ipaH genes, Congo Red absorption ability and by the Sereny test performed on representative strains. Plasmid patterns were heterogeneous but more than 50% of strains were confined to a single pattern. All strains possessed a 1·6 MDa plasmid and 87% of the strains contained a 4 MDa plasmid. Middle-range plasmids (90 MDa to 30 MDa) present in 36% of the strains were not associated with antibiotic resistance. All the strains were clustered within a single type with four subtypes by pulsed-field gel electrophoresis while ribotyping patterns of all the strains were identical.

Zur Frage des Zeitpunktes der Entscheidung zwischen abortivem oder rekombinativem Verhalten eines transduzierten Chromosomenfragmentes in der Empfängerzelle

In wild-type transduction of auxotrophic strain E. coli B/r/thr-1/leu-1/ara-12 colonies auxotrophic for leucine or threonine do not all arise at the same time after plating. In such crosses 48 hrs. after plating from about 20% of minute colonies grown from single abortively transduced cells there can be isolated cells capable to form genetically stable colonies prototrophic for leucine or threonine. Turbidity-measurements on cell populations derived from isolated minute colonies prove that such leu+-cells arise on the plate up to at least 96 hrs. after transduction. Linkage-data of the sites leu+-1 or thr+-1 with ara-12 for these cells disprove the occurence of the thr+ or leu+-state by backmutation. Transduction with E. coli B/r/ara-5 as donor with selection for arabinose-fermentation demonstrates the failure of delayed arising leu+ or thr+-cells in crosses yielding no minute colonies caused by abortive transduction. The experiments are discussed as evidence for the occurence of recombination between the acceptor-chromosome and the abortively transduced chromosomal fragment of a donor cell within a minute colony many cell generations after injection of this fragment.