Monoacylglycerols: glycolipid biosurfactants produced by a thermotolerant yeast, Candida ishiwadae

AIMS: To isolate and characterize biosurfactants produced by a thermotolerant yeast isolated in Thailand. MATERIALS AND RESULTS: Yeast strains isolated from plant material in Thailand were first screened for the ability to produce lipase and biosurfactant. A strain Y12, identified as Candida ishiwadae by physiological tests, survived at 45 degrees C and produced relatively large amounts of biosurfactants. From the culture filtrate of this strain, two glycolipid biosurfactants, a and b, were purified by solvent fractionation, silica gel and ODS column chromatographies. Compounds a and b were determined to be monoacylglycerols; 1-linoleylglycerol and 1-oleylglycerol, respectively. Both compounds exhibited higher surfactant activities tested by the drop collapse test than several artificial surfactants such as sodium dodecyl sulphate. CONCLUSIONS: Glycolipid biosurfactants produced by a thermotolerant yeast, C. ishiwadae were characterized to be monoacylglycerols which exhibited high surfactant activities. SIGNIFICANCE AND IMPACT OF THE STUDY: A thermotolerant yeast strain, C. ishiwadae, could be a potential candidate for producing monoacylglycerols which are useful in industrial applications.     

Chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste

The aim of this work was to study chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste. The culture produced two biosurfactants, a and b, which showed strong activity and were identified as L-rhamnopyranosyl-L-rhamnopyranosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate or Rha-Rha-C10-C10 and L-rhamnopyranosyl-L-rhamnopyranosyl-beta-hydroxydecanoyl-beta-hydroxydodecanoate or Rha-Rha-C10-C12, respectively. Both compounds exhibited higher surfactant activities tested by the drop collapse test than several artificial surfactants such as SDS and Tween 80. Rhamnolipid a showed significant antiproliferative activity against human breast cancer cell line (MCF-7) at minimum inhibitory concentration (MIC) at 6.25 microg/mL while rhamnolipid b showed MIC against insect cell line C6/36 at 50 microg/mL.     

Continuous production of monoacylglycerols from palm olein in packed-bed reactor with immobilized lipase PS

A packed-bed reactor (PBR) system using immobilized lipase PS as biocatalyst was developed for continuous monoacylglycerols (MAG) production. The condition for continuous MAG production using immobilized lipase PS (IM-PS) of 1.5 g (550 U) in PBR (0.68 cm i.d., 25 cm long) was optimized. The effect of molar ratio of glycerol to palm olein, water content in glycerol and residence time on MAG production was investigated. The optimal glycerol to palm olein molar ratio and water content in glycerol were 12:1 and 10% (w/w), respectively. The yield of MAG increased with increasing residence time. At a residence time of 7.5 h gave the highest yield of MAG of 60%. The long-term operation gave the highest yield of MAG 61.5% at 24 h of the operation time with the productivity of 1.61 g MAG/day. A half-life of the long-term process was 35 days of the operation time with the productivity of 0.81 g MAG/day. Furthermore, the large scale of MAG production was performed continuously with IM-PS of 15 g (5500 U) in PBR (1.5 cm i.d., 50 cm long). The highest yield of MAG in large-scale operation of 70.1% and the 11-fold increasing in productivity of 18.3 g MAG/day were obtained at 24 h of the operation time.     

Effects of ozone treatment on cell growth and ultrastructural changes in bacteria

Ozone appeared to inhibit growth and caused the death of gram negative and gram positive tested bacteria: Escherichia coli, Salmonella sp., Staphylococcus aureus and Bacillus subtilis. Bacterial cultures at 10(3), 10(4), 10(5), 10(6), and 10(7) cfu/ml dilution were exposed to 0.167/mg/min/L of ozone at different time intervals (0, 5, 10, 15, 30, 60, 90, 120, and 150 min). Cell viability was observed in all types of tested bacteria at 10(3), 10(4), 10(3) cfu/ml within 30 min after ozone exposure. However, cell inactivation was not significantly observed at concentrations of 10(6), 10(7) cfu/ml even after an exposure of 150 min. Ultrastructural changes of treated bacteria showed deformation, rough damage and surface destruction revealed by scanning electron microscopy. Some bacterial cells showed collapsed and shrunken patterns within 60 min and severe rupture and cellular lysis after 90 min of ozone treatment. This study supports the proposed mechanism of the bacteria inactivation by ozone that caused cell membrane destruction and finally lysis reaction. Thus, the precaution of using ozone as a biocide should be used to address appropriate concentrations of bacterial contamination in water.     

Intensifying Clean Energy Production Through Cultivating Mixotrophic Microalgae from Digestates of Biogas Systems: Effects of Light Intensity,Medium Dilution,and Cultivating Time

High-strength wastewaters after being digested for biogas production in anaerobic digesters still contain substantial nutrients and organics. The anaerobic digestates from four major industries in Thailand were tested with batch cultivation of Chlorella sp. for oil production potentials. Pig farm digestate was found most suitable as the growth medium generating 0.95 g/L_medium (dry biomass), which was 1.16–3.06 times of other digestates tested. Considerable removals of nitrogen and phosphorus achieved were an added benefit to the goal of ultimate treatment of these wastewaters. Light intensity had strong influence on growth and heterotrophic metabolism up to 78 μmol/m²/s, while the dilution of digestate above 2.4× diminished growth potential and lipid production. A quadratic regression model was constructed to describe interaction of light intensity, dilution factor, and time of cultivation to lipid production with a satisfactory precision. Light intensity could influence fatty acid composition, although palmitic acid was found predominant at 47.1 %. The algae oil generated could potentially increase the total energy output from anaerobic digesters of a typical pig farm by 22 %.     

Enhancing Lipid Production from Crude Glycerol by Newly Isolated Oleaginous Yeasts: Strain Selection, Process Optimization, and Fed-Batch Strategy

High lipid-accumulating yeast Trichosporonoides spathulata was newly isolated using crude glycerol as a sole carbon source. After process optimization in a 5-L bioreactor equipped with pH control and aeration system, T. spathulata produced biomass of 11.3 g/L and lipid of 5.01 g/L with a lipid content of 44.3 % using 10 % (w/v) of crude glycerol supplemented only with 0.5 % (w/v) of ammonium sulfate. A one-stage fed-batch feeding with crude glycerol and ammonium sulfate enhanced biomass and lipid production up to 17.3 and 7.25 g/L, respectively, with a lipid content of 41.9 %, while a two-stage fed-batch feeding with only crude glycerol in the second stage led to a lower biomass of 13.8 g/L but a higher lipid production of 7.78 g/L and a higher lipid content of 56.4 %. The fatty acid composition of produced lipid that is similar to plant oil indicates the high potential use of T. spathulata lipid as biodiesel feedstocks.     

A modified approach for high-quality RNA extraction of spore-forming Bacillus subtilis at varied physiological stages

Molecular Biology Reports - High quality RNA is required for the molecular study. Sample preparation of the spore-forming, Gram-positive bacteria like Bacillus sp., remains challenging although...     

Sago starch as a low-cost carbon source for exopolysaccharide production by Lactobacillus kefiranofaciens

Low-cost sago starch was used as a carbon source for production of the exopolysaccharide kefiran by Lactobacillus kefiranofaciens. A simultaneous saccharification and fermentation process of sago starch for kefiran production was evaluated. Factors affecting the process such as an initial pH, temperature, starch concentration, including a mixture of α-amylase and glucoamylase were determined. The highest kefiran concentration of 0.85 g/l was obtained at the initial pH of 5.5, temperature of 30 °C, starch concentration of 4% and mixed-enzymes with activity of 100 U/g-starch. The use of a mixture of α-amylase and glucoamylase could enhance the productivity compared to the use of α-amylase alone. The optimal ratio of α-amylase to glucoamylase of 60:40 gave the highest kefiran production rate of 11.83 mg/l/h. This study showed that sago starch could serve as a low-cost substrate for kefiran production.