Biomedical subjects

L Sembiring

Publications and source records attributed to L Sembiring.

11 recordsLinked to original sources

PubMed2000

Selective isolation and characterisation of members of the Streptomyces violaceusniger clade associated with the roots of Paraserianthes falcataria.

Large numbers of putatively novel streptomycetes were isolated from environmental samples collected from in and around the root system of the tropical angiosperm, Paraserianthes falcataria. Representative isolates were assigned to 37 multi-membered and 107 single membered colour groups based on their ability to form pigments on oatmeal and peptone yeast extract iron agars. The largest taxon, colour group 3, encompassed 94 isolates which had morphological properties typical of members of the Streptomyces violaceusniger clade. Twelve representatives of this taxon chosen on the basis of Curie-point pyrolysis mass spectrometric data were compared with representatives of the validly described species which constitute the Streptomyces violaceusniger clade. Six out of the twelve representative strains were readily distinguished from one another and from the marker strains using a combination of genotypic and phenotypic properties. These organisms were consequently considered to merit species status as Streptomyces asiaticus sp. nov., Streptomyces cangkringensis sp. nov., Streptomyces indonesiensis sp. nov., Streptomycesjavensis sp. nov., Streptomyces rhizosphaerius sp. nov. and Streptomyces yogyakartensis sp. nov.

Bacteriological Techniques↗

PubMed1997

Ester synthesis by NAD(+)-dependent dehydrogenation of hemiacetal: production of methyl formate by cells of methylotrophic yeasts.

A water-soluble ester, methyl formate, was detected as a metabolite in the culture medium of methylotrophic yeasts. Methyl formate synthase, which catalyses NAD(+)-dependent dehydrogenation of the hemiacetal adduct of methanol and formaldehyde, catalyses the ester synthesis. The enzyme activity was induced on a methanol medium and was increased further by the addition of formaldehyde. In the reaction system using intact cells of Pichia methanolica AKU 4262, 135 mM (8.1 g/liter) methyl formate was produced from 2 M methanol. This is a new biological process for ester synthesis that couples spontaneous formation of hemiacetal and alcohol dehydrogenase.

Esters↗

PubMed1995

A novel formaldehyde oxidation pathway in methylotrophic yeasts: methylformate as a possible intermediate.

A considerable amount of methylformate accumulated in the culture medium of methanol-grown methylotrophic yeasts. Methylformate is considered as an intermediate in a novel formaldehyde oxidation pathway. Through investigations with Pichia methanolica, methylformate formation was found to be catalysed by a new type of alcohol dehydrogenase, which was named methylformate synthase. When cells were grown on a relatively high concentration of methanol or exposed to a high concentration of formaldehyde, formation of methylformate was enhanced and the level of methylformate synthase in the cells increased. How methylformate synthase is involved in formaldehyde oxidation and formaldehyde detoxification is discussed.

Alcohol Dehydrogenase↗

PubMed1972