This research investigated the effect of antibacterial activity of Guava leaves extract. Antibacterial activity was determined by agar well diffusion method and test with Staphylococcus aureus Bacillus cereus and Escherichia coli. The results showed that Guava leaves crude extract best inhibited the growth of Bacillus cereus followed by Staphylococcus aureus and Escherichia coli with a mean inhibition zone was 22.0 ±0.3 19.00 ± 0.2 and 14.5 ± 0.3 mm respectively. When comparison antibacterial activity between Guava leaves extract with ampicillin 0.010 mg.

The study aimed to investigate appropriate formula for drinking yoghurt production. The conditions were ratio of yoghurt : concentrated rambutan juice at 100 : 0 90 : 10 85: 20 and 75: 25 the effect of concentrated rambutan juice on physical and chemical and microbiological lactic acid bacteria survival appropriate proportion of syrup and lactic acid bacteria survival during storage of drinking yoghurt from rambutan juice. It was found that proportion of concentrated rambutan juice had no effect in color (L* a*) of the yoghurt (p>0.05) but its impact to b* and viscosity were significant (p≤0.05) they increased with the increased proportion of the concentrated rambutan juice. Yoghurt with 15% concentrated rambutan juice had 88% survival rate of lactic acid bacteria after stimulated digestive system. The results showed that optimal production formula of drinking yoghurt from concentrated rambutan juice and syrup were 90:10 Z(yoghurt: concentrated rambutan juice; 85:15) : syrup) Drinking yoghurt stored in the refrigerator at 4±1oC for 15 day was evaluated and found that LAB survival numbers were 9.90 log CFU/mL.

This research studies the production of bacterial cellulose from Acetobacter xylinum TISTR 975 with pineapple peel juice a low cost carbon source and coconut water as nutrient and carbon source. The factors influencing the production were studied including incubation time type of carbon sources and ratio of mixed carbon sources. In addition the characteristics of the produced bacterial cellulose were investigated using Fourier Transform Infrared Spectrophotometer (FTIR) Scanning Electron Microscope (SEM) Thermogravimetric Analyzer (TGA) Differential Scanning Colorimeter (DSC) and x-ray Diffractometer (xRD). It was found that the coconut water produced the amount of bacterial cellulose higher than the pineapple peel juice with 10 days of production. An addition of the coconut water into the pineapple peel juice increased the amount of bacterial cellulose. The characteristics of two bacterial celluloses from two different sources were nearly similar but the one from the pineapple peel juice had higher impurities. It can be concluded that the pineapple shell extract could be used as low cost carbon source for bacterial cellulose production.

The objectives of this research were to characterize growth and melanin production on different culture media effect of copper ion and cobalt ion on growth and melanin production including antibacterial activity of crude melanin. The results revealed that actinomycetes strain PNST-01 have good growth on ISP-7 medium synthetic medium while strain PRBS-12 grow very well on ISP-3 medium complex medium. Both strains produced high amount of melanin showing brownish colony on ISP-7 medium but there is no melanin pigment production on ISP-1 medium and ISP-6 medium. Moreover the growth rate was reduced and both strains could not produce melanin pigment on ISP-7 medium without supplement with copper chloride and cobalt chloride. Crude melanin extract of strain PNST-01 showed antimicrobial activity against Bacillus cereus ATCC 11778 Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 25923 but could not inhibit Escherichia coli Shigella dysenteriae Salmonella typhi Klebsiella pneumoniae Serratia marcescens Pseudomonas aeruginosa and Streptococcus pyogenes . While crude melanin extract of strain PRBS-12 gave antimicrobial activity only on B. cereus ATCC 11778 and B. subtilis ATCC 6633. Based on the study the results can be used as key information for further development of melanin production and application in various industries.

The objective of this research was to isolate plant growth promoting rhizobacteria from Wedelia trilobata (L.) A.S. Hitchcock rhizosphere and preliminarily test their plant growth promoting properties such as nitrogen fixation siderophore production phosphate solubilization and indole-3-acetic acid production. Forty-seven bacterial isolates were obtained including 26 isolates of gram positive 18 isolates of gram negative and 3 isolates of actinobacteria. After that 8 isolates (including BWTM1_MSU BWTM2_MSU BWTM5_MSU BWTM6_MSU BWWM6_MSU BWWM8_MSU BWWM9_MSU and BWWM16_MSU) were selected for studying on root colonization and plant growth promoting properties under aseptic condition. The results showed that BWTM5_MSU had the evident on the promotion of plant growth with the most percentage of rice seed germination (63.33%) high level of root and shoot length with 6.11 cm and 3.89 cm respectively. As a result the root and shoot fresh weight was as high as 9.56 mg and 11.33 mg respectively. It also correlated with the highest production of indole-3-acetic acid up to 421.29 ug/ml. The root colonization was studied by counting rhizobacteria isolate BWTM5_MSU from rice rhizoplane and rhizosphere with presented bacterial number at 9.67x106 CFU/g root and 1.64x10 10 CFU/g soil respectively.