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-Glutamyl hydrolase with a molecular mass of 28 kDa was purified from the culture broth of Bacillus sp. isolated from Thai Thua-nao, a natto-like fermented soybean food. The purified enzyme hydrolyzed chemically synthesized oligo--L-glutamates but not oligo--D-glutamates and degraded -polyglutamic acid to a hydrolyzed product of only about 20 kDa (with D-and L-glutamic acid in a ratio of 70:30), suggesting that the enzyme is a -glutamyl hydrolase that cleaves theglutamyl linkage between L-and L-glutamic acid ofpolyglutamic acid.

Polyglutamic acid ( -PGA) has been reported to be an effective biosorbent for metal ions. In vitro binding of lead (II) (Pb) by -PGA produced from Bacillus subtilis NBRC16449 was examined and the effect of Pb and -PGA on Brassica chinensis L. grown in the laboratory was investigated. The results revealed that the optimal pH for Pb adsorption was 5.0. -PGA was stable at 35-50°C and pH 5-7. The maximum removal efficiency was 87.9%. Brassica chinensis L. seeds were germinated and grown at 28±1 C on filter paper soaked with Pb solution at 0, 50, 100 and 250 M and -PGA at 0, 100, 500 and 1,000 mg/L for 7 days. The results indicated that Pb markedly inhibited growth of roots by reducing root length (P<0.05). However; the addition of 500 mg/L -PGA significantly protected seedlings from the adverse effects of Pb (P<0.05). Thus, -PGA has high potential as a biopolymer to be used for alleviation of Pb toxicities in plants.

Wide applications of glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D) in rice paddy fields could lead to their residues in environment, posing adverse effects on rice growth and primary producers in the rice ecosystem. This research aims to determine the effects of environmentally relevant concentrations of glyphosate and 2,4-D commercial formulations on Nostoc sp. N1 and rice seedlings. The effects of herbicides on Nostoc sp. N1 were measured from the growth and acute toxicity. The germination and growth were used to determine the effects of herbicides on rice seedlings by measuring their physical and biochemical characteristics. Results showed that while glyphosate had higher toxicity than 2,4-D, both herbicides could stimulate the growth of Nostoc sp. N1 as indicated by their increase in biomass and chlorophyll a content. In Petri dish experiments, Nostoc sp. N1 cells not only promoted the germination of rice seedlings when added alone, but they also alleviated the toxicity of both herbicides to the rice seedlings. In pot experiments, the addition of Nostoc sp. N1 cells combined with herbicides promoted the biochemical characteristics of the rice seedlings by increasing the total chlorophyll, carotenoid and total amino acid content. Our results suggested that environmentally relevant concentrations of glyphosate and 2,4-D formulations should not pose any adverse effects on Nostoc sp. N1. Also, with their toxicity-mitigating and growth-promoting effects on rice seedlings, Nostoc sp. N1 cells could be applied in the alleviation of herbicide residue toxicity in paddy fields.

Zinc oxide-graphitic carbon nitride (ZnO/g-C3N4) composites were synthesized by precipitation method in order to improve photocatalytic activity under visible light. To enhance antimicrobial activity, silver was added into zinc oxide-graphitic carbon nitride (Ag/ZnO/g-C3N4). Ultrastructures of the composite were analyzed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). Photocatalytic activity of the composites was carried out by degradation of methylene blue solution as a function of contact time. The results revealed that ZnO/g-C3N4 was capable of dye degradation at 96.65%. Addition of Ag into ZnO/g-C3N4 resulted in increase of dye reduction rate. For antibacterial test, Ag/ZnO/g-C3N4 exhibited bactericidal activity against Pseudomonas aeruginosa and Bacillus cereus. For antifungal test, Ag/ZnO/g-C3N4 showed resistance to Aspergillusniger for 7 days. Ag/ZnO-g-C3N4 composite exhibited better photocatalytic and antimicrobial activities compare to ZnO and g-C3N4. These results indicate that precipitation method is a cheap, rapid and efficient method that can be used to synthesize Ag/ZnO-g-C3N4 composites. For further studies, applications of this Ag/ZnO-g-C3N4 composites in microbiological and agricultural fields will be carried out.