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The research was conducted to understand the diversity of microbial communities in the rice cultivars KDM 105 in the rice fields at Sanamchaikate, Chachoengsao Province. The culturing bacterial community in paddy soil before planting, during the planting and sowing of rice, and after rice collection as well as isolation of free nitrogen fixing bacteria under aerobic and anaerobic conditions were identified by molecular comparision of 16S small subunit rRNA genes as well as species diversity and their richness by Most Probable Number (MPN) method. Culturable bacterial isolates in the soil around the roots of rice varieties were determined for their physical appearances on the solid culture (Plate culturing method) and the microscopic observation under light microscope. It was found that bacteria in the paddy soil complemented with organic fertilizers and no pesticide application for over five years had a pH range from 5.2 to 5.5 cultivated jasmine rice, 8-9 log Units of free N2-fixing bacteria near the roots compared with those in other area having 4-5 log Units. Most of them were identified to be Pseudomonas sp. Microbacterium sp. Bacillus sp. Stenotrophomonas sp. and Burkholderia sp., by homology comparison of 16S rDNA gene at 98, 97, 99, 99.5, and 99%, respectively. This research revealed the recognizable complex and change in soil bacteria presented in paddy ecosystem. In any critical change of to the soil, the study of microbial diversity, compositions and their richness can be further useful for indicating proper soil management.

Since the green chemistry strategy of the use of biological process is well known for its safe, easy, nontoxic, biocompatible and especially environmental friendly to all users. Recently, more nanomaterials synthesized by the uses of plants and/ or microorganisms are applied in many areas such as electronics, nanotechnology. Especially they are used to synthesize novel materials with unique properties and purposes. In this study, the researchers aimed to isolate microorganisms with the capability in gold nanoparticles (AuNPs) synthesis from the sources that are from gold management process such as leaching and washing process in gold/ jewelry carving factory. Three isolated genera composed of bacteria, yeasts, fungi synthesizing intracellular AuNOs were obtained and characterized for their species by PCR amplification of rDNA genes and sequence analysis and comparisons. They were Pseudomonas sp., Verticillium sp., Aspergillus sp., and Saccharomyces sp. The factors including pH, temperature, reducing agents, duration of AuNP formation were determined. The predominantly extracellular gold formation as a major criterion for synthesis of AuNPs was also chosen. The obtained isolates can be certain potential in future practical application in harvesting AuNPs from the waste water in most gold carving factory.

The silver refinery is very important for west management in the jewelry industry. In this work, we proposed the alternative of silver refinery process by using microorganism pathway. We focused on the isolation of microorganism which was found from manufacturing process and forming in gems and jewelry industry. Results showed that the initial silver refinery microorganism performed only in terms of Pseudomonas genus especially in AgNO3 solution. In contrast, Bacillus genus was not clearly effective silver refinery. These results could be the basis information to establish and develop system for silver refinery and/or silver quality improvement with biological process in future.