Use of whey lactose from dairy industry for economical kefiran production by Lactobacillus kefiranofaciens in mixed cultures with yeasts.

To evaluate the feasibility of producing kefiran industrially, whey lactose, a by-product from dairy industry, was used as a low cost carbon source. Because the accumulation of lactic acid as a by-product of Lactobacillus kefiranofaciens inhibited cell growth and kefiran production, the kefir grain derived and non-derived yeasts were screened for their abilities to reduce lactic acid and promote kefiran production in a mixed culture. Six species of yeasts were examined: Torulaspora delbrueckii IFO 1626; Saccharomyces cerevisiae IFO 0216; Debaryomyces hansenii TISTR 5155; Saccharomyces exiguus TISTR 5081; Zygosaccharomyces rouxii TISTR 5044; and Saccharomyces carlsbergensis TISTR 5018. The mixed culture of L. kefiranofaciens with S. cerevisiae IFO 0216 enhanced the kefiran production best from 568 mg/L in the pure culture up to 807 and 938 mg/L in the mixed cultures under anaerobic and microaerobic conditions, respectively. The optimal conditions for kefiran production by the mixed culture were: whey lactose 4%; yeast extract 4%; initial pH of 5.5; and initial amounts of L. kefiranofaciens and S. cerevisiae IFO 0216 of 2.1×10(7) and 4.0×10(6)CFU/mL, respectively. Scaling up the mixed culture in a 2L bioreactor with dissolved oxygen control at 5% and pH control at 5.5 gave the maximum kefiran production of 2,580 mg/L in batch culture and 3,250 mg/L in fed-batch culture.

Recent advances in mycobacterial cell wall glycan biosynthesis.

The cell wall of mycobacteria, including the causative agents of the human diseases tuberculosis (Mycobacterium tuberculosis) and leprosy (M. leprae), is composed of an array of carbohydrate-containing molecules. These glycoconjugates are assembled by glycosyltransferases (GTs) that work in tandem through pathways that are only now beginning to be fully understood. Given the essentiality of cell wall glycans to mycobacterial viability, these enzymes represent novel targets for drug action. Summarized here are recent genetic and biochemical studies leading to the identification and characterization of mycobacterial GTs.