Diversity and characterization of cultivable oleaginous yeasts isolated from mangrove forests

A total of 198 yeasts were isolated from 140 samples collected from 7 mangrove forests in 4 provinces of Thailand, and were found to belong to 30 genera, 45 described species and at least 12 undescribed species based on their 26S rRNA (D1/D2 domain) gene sequence. The most prevalent species was Candida tropicalis, followed by Candida pseudolambica and Rhodosporidium paludigena. Lipid accumulation, as determined by Nile red staining, of the isolated yeasts revealed that 69 and 18 strains were positive and strongly positive, respectively, while quantitative analysis of the intracellular lipid accumulated in the latter indicated that 10 of these strains, Pseudozyma tsukubaensis (YWT7-2 and YWT7-3), Rhodotorula sphaerocarpa (YWW6-1 and SFL14-1SF), Saitozyma podzolica (YWT1-1, NS3-3 and NS10-2), Prototheca zopfii var. hydrocarbonea OMS6-1 and Prototheca sp. (YMTW3-1 and YMTS5-2), were oleaginous. In this study we found that under nitrogen depletion condition (155 C/N ratio) Pseudozyma tsukubaensis YWT7-2 accumulated the highest level of intracellular lipid at 32.4% (w/w, dry cell weight), with a broadly similar fatty acid composition to that in palm oil.     

Isolation and characterization of arsenic resistant bacteria from tannery wastes and agricultural soils in Thailand

Highly arsenic resistant bacteria (27 isolates), which had a minimum inhibitory concentrations (MICs) for arsenite and arsenate of ? 40 mM and > 400 mM, respectively, were isolated from tannery wastes and agricultural soils collected in Central Thailand. On the basis of the morphological, cultural, physiological and biochemical characteristics, and on the principal ubiquinone component and 16S rRNA gene sequence analyses, they were identified as nine isolates each ofKlebsiella (Groups 1 and 8) andAcinetobacter (Groups 2, 3 and 7), four isolates each ofPseudomonas (Groups 4 and 6) andComamonas (Group 5), and one isolate ofEnterobacter (Group 9). From these 27 isolates, only one isolate, A3-3 from the genusComamonas, appeared potentially capable of oxidizing arsenite to arsenate, as determined by silver nitrate staining of arsenite agar plates after colony growth.     

Co-fermentation of cassava waste pulp hydrolysate with molasses to ethanol for economic optimization

Cassava waste pulp (CWP)–enzymatic hydrolysate was co-fermented with molasses (CWP-EH/molasses mixture) with the aim to optimize ethanol production by Saccharomyces cerevisiae TISTR 5606 (SC 90). The optimal fermentation conditions for ethanol production using this mixture were 245 g/L initial total sugar supplemented with KH₂PO₄ (8 g/L), at 30 °C for 48 h of fermentation under an oxygen-limited condition with agitation at 100 rpm, producing an ethanol concentration of 70.60 g/L (0.31 g ethanol/g total sugar). The addition of cassava tuber fiber (solid residue of CWP after enzymatic hydrolysis) at 30 g/L dry weight to the CWP-EH/molasses mixture increased ethanol production to 74.36 g/L (0.32 g ethanol/g total sugar). Co-fermentation of CWP-EH with molasses had the advantage of not requiring any supplementation of the fermentation mixture with reduced nitrogen.     

Isolation and characterization of arsenite-oxidizing bacteria from arsenic-contaminated soils in Thailand

Two hundred and eighty-eight arsenic-resistant bacteria were isolated by an enrichment culture method from a total of 69 arsenic-contaminated soil-samples collected from Dantchaeng district in Suphanburi province (47 samples), and from Ron Phiboon district in Nakhon Sri Thammarat province (22 samples), in Central and Southern Thailand, respectively. Twenty-four of the 288 isolated arsenic-resistant bacteria were found to be arsenite-oxidizing bacteria. On the basis of their morphological, cultural, physiological, biochemical and chemotaxonomic characteristics, and supported by phylogenetic analysis based upon their 16S rRNA gene sequences, they were divided into five groups, within the genera Acinetobacter, Flavobacterium, Pseudomonas, Sinorhizobium and Sphingomonas, respectively. Within genera, phylogenetic analysis using the 16S rRNA gene sequences suggested that they were comprised of at least ten species, five isolates being closely related to known bacteria (Acinetobacter calcoaceticus NCCB 22016^T, Pseudomonas plecoglossicida FPC951^T, Ps. knackmussii B13^T, Sinorhizobium morelense Lc04^T, and Sphingomonas subterranea IFO16086^T). The other five proposed species are likely to be new species closely related to Flavobacterium johnsoniae, Sinorhizobium morelense, Acinetobacter calcoaceticus and Pseudomonas plecoglossicida, but this awaits further characterization for confirmation of the taxonomic status. No overlap in isolated species or strains was observed between the two sites. The strain distribution and characterization are described.     

Flavobacterium arsenitoxidans sp. nov., an arsenite-oxidizing bacterium from Thai soil

An arsenite-oxidizing bacterium, strain S2-3H^T, was isolated from arsenic-contaminated soil sample collected from Dantchaeng district, Suphanburi province, Thailand and was characterized based on polyphasic taxonomic study. The strain was observed to be a Gram-stain negative, aerobic, yellow pigmented, non-spore forming and rod-shaped bacterium. Major menaquinone was MK-6. Iso-C_15:0, iso-C_15:0 3OH, C_16:1 ω7c/C_16:1 ω6c, C_16:0, iso-C_17:0 3OH, and C_16:0 3OH were the predominant cellular fatty acids. The polar lipid profile consisted of phosphatidylethanolamine, unidentified phospholipids and unidentified aminophospholipids. The DNA G+C content was 37.0 mol%. Phylogenetic analysis using 16S rRNA sequence showed that strain S2-3H^T is affiliated to the genus Flavobacterium, and is closely related to F. defluvii KCTC 12612^T (97.0 %) and F. johnsoniae NBRC 14942^T (97.0 %). The strain S2-3H^T could be clearly distinguished from the related Flavobacterium species by its physiological and biochemical characteristics as well as its phylogenetic position and DNA–DNA relatedness. Therefore, the strain represents a novel species of the genus Flavobacterium, for which the name Flavobacterium arsenitoxidans sp. nov. (type strain S2-3H^T = KCTC 22507^T = NBRC 109607^T = PCU 331^T = TISTR 2238^T) is proposed.     

Autolysis of Bacillus subtilis induced by monovalent cations

Summary Resting cell suspensions of seven Nocardia species catalyzed the production of 10-hydroxystearic acid from oleic acid. Nocardia cholesterolicum NRRL 5767 gave a good yield with optimum conditions at pH 6.5 and 40°C. Yields exceeding 90% can be obtained within 6 h with 0.1 g cells (dry weight) and 178 mg oleic acid in 10 ml of 0.05 M sodium phosphate buffer (pH 6.5). In addition, minor amounts of 10-ketostearic acid were formed as a by-product. The reaction proceeded via hydration of the double bond as shown by labeling experiments with deuterium oxide and ¹⁸O-labeled water. The system was specific for fatty acids with cis unsaturation at the 9 position.A part of this paper was presented at a poster session at the World Conference on Biotechnology for the Fats and Oils Industry, Hamburg, Federal Republic of Germany, September 1987, and at the 194th National American Chemical Society Meeting, New Orleans, September 1987RetiredThe mention of firm names or trade products does not imply that they are endorsed or recommended by USDA over other firms or similar products not mentioned