Fresh juice from C grade longan (mg/g fresh fruit; total sugars 51.6 ± 0.5, nitrogen 0.021 ± 0.004; gallic acid 0.025 ± 0.001; ellagic acid 0.016 ± 0.001) with addition of 8.52 g ammonium sulfate/l was the optimal medium for cultivation processes of Saccharomyces cerevisiae TISTR 5606 and Candida tropicalis TISTR 5306 capable of producing ethanol and phenylacetylcarbinol (PAC) among five longan grades. S. cerevisiae TISTR 5606 produced ethanol (33.4 ± 3.2 g/L) at a significantly higher level (p ≤ 0.05) than C. tropicalis TISTR 5306 (22.3 ± 1.1 g/L) with similar ethanol yields (Yp/s) between 0.21 and 0.22 g ethanol produced/g sugars consumed. Whole cells of C. tropicalis TISTR 5306 produced a significantly higher (p ≤ 0.05) PAC level (27.2 ± 0.7 mM) than S. cerevisiae TISTR 5606 (3.59 ± 1.33 mM) after 6 hr in an equivalent volume biphasic biotransformation system. Practical applications Longan is one of the important economic fruit of Thailand with production volume in 2017 reaching one million tons. Less than 10% of these are domestically consumed while more than 90% are exported to several countries whose population frequently consume longan as a nutritious food supplement. This study can help solving overproduction problem of longan fruit by processing C grade fresh longan, which is accounted for 5% of the overall production volume, in the form of juice extract with the relatively high sugars content. Microbial fermentation of this juice and subsequent whole cells biotransformation process result in ethanol and PAC, respectively. Ethanol can be used as an alternative biofuel or important industrial solvent while PAC is a precursor for production of commercial nasal decongestant (ephedrine) or anti‐asthmatic compound (pseudoephedrine).

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Lactobacillus casei TISTR 1500 was isolated from soil of a dairy wastewater treatment plant and selected as the most active azo dye degrader of 19 isolates. Growing cells and freely suspended cells of this strain completely degraded methyl orange, thereby decolorizing the medium. The strain stoichiometrically converted methyl orange to N,N-dimethyl-p-phenylenediamine and 4-aminobenzenesulfonic acid, which were identified by HPLC, GC, and GC-MS analyses. The enzyme activity responsible for the cleavage of the azo bond of methyl orange was localized to the cytoplasm of cells grown on modified MRS medium containing methyl orange. The effect of sugars, oligosaccharides, organic acids, metal ions, pHs, oxygen and temperatures on methyl orange decolorization by freely suspended cells was investigated. The optimal conditions for the decolorization of methyl orange by the Lactobacillus casei TISTR 1500 are incubation at 35 degrees C and pH 6 with sucrose provided as the energy source.

Hot extraction with acetone was the most efficient method for the extraction of fucoxanthin from Phaeodactylum tricornutum. The purified compound resulted in three main peaks consisted of the trans form along with two isomers. The structure of microalgal fucoxanthin was similar to that of brown seaweed, but the ratio of trans-to cis-form was different. The ratio of the cis-form increased as the extraction temperature increased. Fucoxanthin was unstable at high temperature, in acidic condition, and after long period of storage. Fucoxanthin exhibited strong activity against BChE, with an IC 50 value of 1.97 mM and mixed inhibition type, whereas it had weak activity against AChE. The IC 50 value on reducing power was 0.01 mM, which was much stronger than those of the positive controls. When the amount of cis-isomer increased by 2%, the scavenging activity against DPPH, hydrogen peroxide, superoxide anion, and reducing power decreased by 21.0, 10.3, 16.0, and 19.7%, respectively. Therefore, fucoxanthin could be a useful approach for Alzheimer's disease treatment.

Candida tropicalis TISTR 5350 was used in the comparison of seven concentration levels of silver nanoparticles (0, 5, 10, 15, 20, 25, and 30 μg ml -1 ) for cell disruption methods. The optimized cell disruption strategy was selected based on the optimal protein yield and biological activity. The maximum volumetric and specifi c pyruvate decarboxylase (PDC, EC 4.1.1.1) activities (0.53±0.05 U ml -1 and 0.17±0.02 U mg -1 protein, respectively) were observed at 15 μg ml -1 silver nanoparticles. The silver nanoparticle concentration level of 15 μg ml -1 was investigated further by comparing the reaction mixtures at different time intervals of 0, 1, 2, 3, 4, 5, and 6 min. The result showed that the highest specifi c PDC activity of 0.39±0.01 U mg -1 protein was obtained from mixing for 3 min. This was not signifi cantly different (P≤0.05) from other mixing time intervals.