• KSBB Journal
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• v.25 no.1
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• pp.79-84
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• 2010

In the present study, we isolated a new bacterial strain producing invertase (EC 3.2.1.26) and determined optimized culture condition in flask culture. The strain was identified as Bacilus flexus determined by the 16S rDNA sequencing method. The invertase was produced only in the sucrose medium as the sole carbon source. Potassium nitrate was an adequate nitrogen source for enzyme production, whereas meat peptone showed the highest bacterial growth. Enzyme production was increased about 2-fold when $MgSO_4\cdot7H_2O$ was supplemented to the growth media. The optimum temperature was found to be $30^{\circ}C$ for both enzyme production and bacterial growth. Invertase exhibited pH optima in the range 5.0-6.0 and have a temperature optimum at $40^{\circ}C$, similarly to other invertases found from different microbial sources. Several mineral ions (K and Fe) stimulated the invertase activity, whereas some bioelements (Ag, Mg, and Mn) inhibited enzyme activity. Under the optimized culture condition, the maximum enzyme production (over 250 units/mL) was achieved at 20 h. To the best of our knowledge, this is the first time to report on invertase production by Bacilus flexus.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.3
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• pp.372-377
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• 2001

A study on the prevalence and causes of sub-clinical mastitis was conducted on ten smallholder and large-scale dairy farms in Morogoro urban and peri-urban areas. A total of 65 lactating cows were screened using the California Mastitis Test (CMT). Confirmatory tests used included; the direct microscopic somatic cell count (DMSCC), culture, bacteriological and biochemical tests. Structured questionnaires were used to collect information on management aspects. Results showed 62% and 4% cows as sub- clinical and clinical mastitis cases respectively. Levels of infection were higher on smallholder farms (75%) than on large-scale farms (25%). All tested cows had high cell counts (>500,000) per ml of milk. Incidences of mastitis were significantly (p<0.05) related to milking practices. The dominant bacterial isolates in the same order were Staphylococcus aureus, Streptococcus spp, and Escherichia coli. Other organisms isolated included Pseudomonas spp and Klebsiella spp. It was concluded that the high rates of sub-clinical mastitis in the research area were mainly due to poor management and unhygienic milking practices.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.10
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• pp.1477-1482
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• 2001

Research in low cost feeds with high nutritional value and immunogenicity is important to reduce production cost and increase yields in the shrimp industry. In this study, immunostimulants of bacterial origin (peptidoglycan and lipopolysaccharides) and egg white were incorporated in shrimp diets as feed additives to determine the growth, survival and tolerance of Penaeus monodon to white spot syndrome virus (WSSV). Although the results obtained were not statistically significant (p>0.05) among the treatments, shrimp fed with bacterial additives and egg white showed higher weight gain, specific growth rate and survival than those fed on commercial shrimp diet. Shrimp fed with artificial diet showed 100% mortality when challenged with WSSV. However, shrimp fed on peptidoglycan supplemented diet had higher survival than their counterpart, whereas shrimp fed on egg white supplemented diet had a higher specific growth rate and better tolerance when challenged with WSSV. Further studies are required to determine the effectiveness and optimization of bacterial strains and egg white as feed additives to increase production and enhance the shrimp immune response to diseases.

• Korean Chemical Engineering Research
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• v.44 no.1
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• pp.52-57
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• 2006

Bacterial cellulose (BC) was produced by Gluconacetobacter hansenii PJK (KCTC 10505 BP) strains using the waste of beer fermentation broth. It contained more C and N than a basal medium with a small amount of S and more than 4％ ethanol. The amount of BC produced in a shaking culture using the waste of beer fermentation broth was nearly the same as that of a basal medium. The production of BC decreased in a shear stress field in a jar fermenter although the conversion of cellulose producing ($Cel^+$) cells to non-cellulose producing ($Cel^-$) mutants was not severe. This study showed that the waste of beer fermentation broth is an inexpensive carbon, nitrogen source with ethanol and thus a worthy substitute for the conventional medium for BC production.

• Korean Journal Plant Pathology
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• v.14 no.2
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• pp.177-183
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• 1998

A DNA fragment which is involved in tolassin production was cloned to obtain a molecular marker of Pseudomonas tolaasii, a casual agent of bacterial brown blotch disease of oyster mushroom (Pleurotus ostreatus). Tolaasin is a lipodepsipeptide toxin and known as a primary disease determinant of the P. tolaasii. It is responsible for formation of white line in agar when P. tolaasii were cultured against white line reacting organisms (WLROs). White line negative mutants (WL-) were generated by conjugation between rifampicin resistant strain of P. tolaasii and E. coli carrying suicidal plasmid pSUP2021 : : Tn5. The ability of tolaasin production of the WL- mutants was examined by hemolysis test, pathogenicity test, and high pressure liquid chromatography (HPLC) analysis of culture filtrate. All of the WL- mutants were lost the ability of tolaasin production (Tol-). Genomic library of the Tol- mutant was constructed in pLAFR3 and the cosmid clone containing Tn5 was selected. DNA fragment fro franking region of Tn5 was cloned from the plasmid and used as a probe in Southern blot. DNA-DNA hybridization with the probe to total DNA from group of bacteria ecologically similar to P. tolaasii including WLORs, fluorescent Pseudomonads isolated from oyster mushroom, P. agarici, P. gingeri, and some of other species of Psedomonas showed that some of the tested bacteria do not have any hybridized band and others have bands sowing RFLP. The cloned DNA fragment or its nucleotide sequence will be useful in detection and identification of the P. tolaasii.

• Microbiology and Biotechnology Letters
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• v.50 no.1
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• pp.81-88
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• 2022

Acetic acid bacteria (AAB) are versatile organisms involved in the production of variety of fermented foods, such as vinegar and kombucha, and products of biotechnological relevance, such as bacterial cellulose. In the present study, Malatya apricot, a variety with protected designation of origin (PDO), and vinegar samples produced using various fruits were used to isolate AAB. The 19 AAB isolates obtained were typed using (GTG)5 fingerprinting, and the ones selected were identified by sequencing either 16S rDNA alone or in combination with 16S-23S rRNA internal transcribed spacer region or ligA gene. While all apricot isolates (n = 10) were Gluconobacter cerinus, vinegar isolates (n = 9) were composed of Komagataeibacter saccharivorans, Acetobacter syzygii, and possible two new species of AAB, Komagataeibacter sp., and Gluconobacter sp. (GTG)5 fingerprinting showed the presence of several genotypes of G. cerinus in the apricot samples. Screening for some technologically relevant properties, including thermotolerance, ethanol tolerance, and cellulose production capability, showed that all Komagataeibacter and some Gluconobacter isolates could tolerate the temperature of 35℃, and that vinegar isolates could tolerate up to 8% ethanol. One isolate, Komagataeibacter sp. GUS3 produced bacterial cellulose (1 g/l) and has the potential to be used for cellulose production.

• Journal of Microbiology and Biotechnology
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• v.34 no.6
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• pp.1314-1321
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• 2024

Branched-chain hydroxy acids (BCHAs), produced by lactic acid bacteria, have recently been suggested as bioactive compounds contributing to the systemic metabolism and modulation of the gut microbiome. However, the relationship between BCHAs and gut microbiome remains unclear. In this study, we investigated the effects of BCHAs on the growth of seven different families in the gut microbiota. Based on in vitro screening, both 2-hydroxyisovaleric acid (HIVA) and 2-hydroxyisocaproic acid (HICA) stimulated the growth of Lactobacillaceae and Bifidobacteriaceae, with HIVA showing a significant growth promotion. Additionally, we observed not only the growth promotion of probiotic Lactobacillaceae strains but also growth inhibition of pathogenic B. fragilis in a dose-dependent manner. The production of HIVA and HICA varied depending on the family of the gut microbiota and was relatively high in case of Lactobacillaceae and Lachnosporaceae. Furthermore, HIVA and HICA production by each strain positively correlated with their growth variation. These results demonstrated gut microbiota-derived BCHAs as active metabolites that have bacterial growth modulatory effects. We suggest that BCHAs can be utilized as active metabolites, potentially contributing to the treatment of diseases associated with gut dysbiosis.

• Journal of Microbiology and Biotechnology
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• v.34 no.1
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• pp.29-38
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• 2024

Chemical and physical elements affecting the production of bacterial extracellular vesicles (BEVs) of the human pathogen Vibrio vulnificus were quantitatively assessed to optimize the conditions for the BEV production by using the western blot quantification for an outer membrane porin OmpU and by fluorescent dye FM4-64. When cells were cultured at 37℃ in an enriched medium (2 × Luria Bertani; 2 × LB) in the presence of EDTA, they produced about 70% more BEVs. BEVs were purified from the cells cultured in the established optimal conditions by the density gradient ultracentrifugation. The dynamic light scattering measurement of the purified BEVs showed that the diameter of them ranged from approximately 25 nm to 161 nm. We hypothesized that there may be some features in nucleotide sequences specific to RNAs packaged in BEVs compared to those in cellular RNA molecules. We compared the nucleotide sequences and abundance of sRNAs between in the cellular fraction and in BEVs through next-generation sequencing (NGS). While no distinct feature was observed in the nucleotide sequences of sRNAs between two groups, the length of sRNA fragments from BEVs were significantly shorter than those in cytoplasm.

• Journal of Microbiology and Biotechnology
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• v.32 no.5
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• pp.621-629
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• 2022

Bacterial outer membrane vesicles (OMVs) typically contain multiple immunogenic molecules that include antigenic proteins, making them good candidates for vaccine development. In animal models, vaccination with OMVs has been shown to confer protective immune responses against many bacterial diseases. It is possible to genetically introduce heterologous protein antigens to the bacterial host that can then be produced and relocated to reside within the OMVs by means of the host secretion mechanisms. Accordingly, in this study we sought to develop a novel platform for recombinant OMV (rOMV) production in the widely used bacterial expression host species, Escherichia coli. Three different lipoprotein signal peptides including their Lol signals and tether sequences-from Neisseria meningitidis fHbp, Leptospira interrogans LipL32, and Campylobactor jejuni JlpA-were combined upstream to the GFPmut2 model protein, resulting in three recombinant plasmids. Pilot expression studies showed that the fusion between fHbp and GFPmut2 was the only promising construct; therefore, we used this construct for large-scale expression. After inducing recombinant protein expression, the nanovesicles were harvested from cell-free culture media by ultrafiltration and ultracentrifugation. Transmission electron microscopy demonstrated that the obtained rOMVs were closed, circular single-membrane particles, 20-200 nm in size. Western blotting confirmed the presence of GFPmut2 in the isolated vesicles. Collectively, although this is a non-optimized, proof-of-concept study, it demonstrates the feasibility of this platform in directing target proteins into the vesicles for OMV-based vaccine development.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.6
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• pp.900-905
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• 2009

We analyzed succession of the bacterial communities during composting of animal manure in three individual facilities. Polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) targeting for the bacterial 16S rRNA gene were used to clarify the changes of bacterial community throughout each composting process. Our study revealed that the bacterial community structures differed during the composting process. The bacterial community in composting of facility A showed little change throughout the process. In the compost sample from facility B, its community had a small shift as the temperature increased. In compost from facility C, the temperature dynamically changed; it was shown that various bacterial communities appeared and disappeared as follows: in the initial phase, the members of phylum Bacteroidetes dominated; in the thermophilic phase, some bacteria belonging to phylum Firmicutes increased; towards the end, the community structure consisted of three phyla, Bacteroidetes, Firmicutes, and Proteobacteria. This study provides some information about the bacterial community actually present in field-scale composting with animal manure.