The aim of this study was to investigate the antimicrobial potential of actinomycetes isolated from combs of the giant honey bee, Apis dorsata. In total, 25 isolates were obtained from three different media and were screened for antimicrobial activity against four plant pathogenic bacteria (Ralstonia solanacearum, Xanthomonas campestris pv. campestris, Xanthomonas oryzae pv. oryzae and Pectobacterium carotovorum). Following screening using a cross-streaking method, three isolates showed the potential to inhibit the growth of plant pathogenic bacteria. Based on a 96-well microtiter assay, the crude extract of DSC3-6 had minimum inhibitory concentration (MIC) values against X. oryzae pv. oryzae, X. campestris pv. campestris, R. solanacearum and P. carotovorum of 16, 32, 32 and 64 mg L−1, respectively. The crude extract of DGA3-20 had MIC values against X. oryzae pv. oryzae, X. campestris pv. campestris, R. solanacearum and P. carotovorum of 32, 32, 32 and 64 mg L−1, respectively. The crude extract of DGA8-3 at 32 mgL−1 inhibited the growth of X. oryzae pv. oryzae, X. campestris pv. campestris, R. solanacearum and P. carotovorum. Based on their 16S rRNA gene sequences, all isolates were identified as members of the genus Streptomyces. The analysis of 16S rRNA gene sequence similarity and of the phylogenetic tree based on the maximum likelihood algorithm showed that isolates DSC3-6, DGA3-20 and DGA8-3 were closely related to Streptomyces ramulosus (99.42%), Streptomyces axinellae (99.70%) and Streptomyces drozdowiczii (99.71%), respectively. This was the first report on antibacterial activity against phytopathogenic bacteria from actinomycetes isolated from the giant honey bee.

An experiment using a standard strain of Lactobacillus amylovorus TISTR1110 to test for the capability of carbohydrate utilisation of nine cultivars of rice found that L. amylovorus TISTR1110 could utilise carbohydrate from all cultivars and also exhibit nonhaemolytic properties. After testing the viability of the strain under simulated gastrointestinal tract conditions by enumeration after 5 h, the results showed that the amount of L. amylovorus TISTR1110 present was 4.0 9 10 5 CFU/mL or a 73.78% survival rate. From the evaluation of Thai rice cultivars as carriers in probiotic products, the highest amount of probiotic bacteria was found in baked and encapsulated glutinous Luem Pua Thai sticky rice up to 4.9 9 10 6 CFU/g or a survival rate of 69.39 AE 0.06%. The second highest rate (4.8 9 10 5 CFU/g) was found in heat-moisture steamed rice of Riceberry rice cultivar or a survival rate of 59.74 AE 0.11%. After testing the capability of adherence using SEM, the results showed that glutinous Luem Pua sticky rice resulted in considerably high survival rate of probiotic bacteria compared with other rice. Additionally, the microbiological safety test reported that the amounts of contaminants were acceptable.

This study aimed to investigate cultivable actinomycetes associated with rare honey bee species in Thailand and their antagonistic activity against plant pathogenic bacteria. Actinomycetes were selectively isolated from the black dwarf honey bee (Apis andreniformis). A total of 64 actinomycete isolates were obtained with Streptomyces as the predominant genus (84.4%) followed by Micromonospora (7.8%), Nonomuraea (4.7%) and Actinomadura (3.1%). All isolates were screened for antimicrobial activity against Xanthomonas campestris pv. campestris, Pectobacterium carotovorum and Pseudomonas syringae pv. sesame. Three isolates inhibited the growth of X. campestris pv. campestris during in vitro screening. The crude extracts of two isolates (ASC3-2 and ASC5-7P) had a minimum inhibitory concentration (MIC) of 128 mg L−1against X. campestris pv. campestris. For isolate ACZ2-27, its crude extract showed stronger inhibitory effect with a lower MIC value of 64 mg L−1 against X. campestris pv. campestris. These three active isolates were identified as members of the genus Streptomyces based on their 16S rRNA gene sequences. Phylogenetic analysis based on the maximum likelihood algorithm showed that isolate ACZ2-27, ASC3-2 and ASC5-7P were closely related to Streptomyces misionensis NBRC 13063T (99.71%), Streptomyces cacaoi subsp. cacaoi NBRC 12748T (100%) and Streptomyces puniceus NBRC 12811T (100%), respectively. In addition, representative isolates from non-Streptomyces groups were identified by 16S rRNA gene sequence analysis. High similarities were found with members of the genera Actinomadura, Micromonospora and Nonomuraea. Our study provides evidence of actinomycetes associated with the black dwarf honey bee including members of rare genera. Antimicrobial potential of these insect associated Streptomyces was also demonstrated especially the antibacterial activity against phytopathogenic bacteria.

Background: Thailand is one of the most bio-diversified countries in Southeast Asia, especially regarding plants, animals and microbes that impact directly on human and animal life. Methods: Of the 201 bacterial isolates that were screened from Thai rice and bees in Ratchaburi and Chiang Mai provinces, Thailand, most were classified in the genus Bacillus. Result: From the morphological test and 16S ribosomal DNA sequence study, three strains, Bacillus flexus KRptI_S2, Microbacterium paraoxydans C13HN2 and Paenibacillus hunanensis KRrb_T2, could produce amylase and protease enzyme and non-hemolytic activity at higher temperature. The highest enzymatic activity of protease was produced by P. hunanensis KRrb_T2 (378.9967±1.335 U.mL -1 ) at 36 h. Conclusion: In summary, the bacteria from Thai rice and bees could be potential suitable sources of protease production for development by the food and beverage industries globally.

Based on testing inhibition to nine strains of pathogens in the gastrointestinal tract, Lacticaseibacillus rhamnosus KPS‐VE9 inhibited the growth of Aeromonas hydrophila, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Serratia marcescens, Staphylococcus aureus, Vibrio parahaemolyticus, and Candida albicans, whereas Bacillus coagulans KPS‐TF02 inhibited only V. parahaemolyticus when performed in brain–heart infusion agar. When these two strains of probiotics were tested using ABTS+ scavenging assay, B. coagulans KPS‐TF02 and L. rhamnosus KPS‐VE9 produced good levels of antioxidants, with their antioxidant activities at 1.50 and 2.00 mg Trolox equivalent/μl, respectively. B. coagulans KPS‐TF02 survived well under simulated gastric and small intestine conditions with higher survival rates when the bacterium was mixed in rice‐based carriers, whereas L. rhamnosus KPS‐VE9 had a high survival rate only under simulated gastric conditions without rice. However, in probiotic rice products, the survival rate after storage at 4°C for 6 months was higher than that at 25°C for both probiotic strains, being only L. rhamnosus KPS‐VE9 able to maintain counts higher than 106 CFU/g at the end of the storage period. No microbial contamination was observed for the rice capsules studied. The survival rates of the probiotics studied in the rice capsules when submitted to the simulated gastrointestinal conditions were, therefore, not directly correlated to their initial counts in these products. Novelty impact statement This is the first report of an application of mixed cultivars of Thai‐pigmented rice and mixed culture probiotics as a novel dried‐formulated probiotic product. This research investigated the probiotic properties of two probiotic bacteria (Bacillus coagulans KPS‐TF02, and Lacticaseibacillus rhamnosus KPS‐VE9) in developing novel probiotic products using Thai‐pigmented rice (purple, red, and yellow color) as a carrier. Probiotics have antibacterial activity and show high antioxidant activities.