Members of the genus Bacillus are considered to be both, among the best studied and most commonly used bacteria as well as the most still unexplored and the most wide-applicable potent bacteria because novel Bacillus strains are continuously being isolated and used in various areas. Production of optically pure l-lactic acid (l-LA), a feedstock for bioplastic synthesis, from renewable resources has recently attracted attention as a valuable application of Bacillus strains. l-LA fermentation by other producers, including lactic acid bacteria and Rhizopus strains (fungi) has already been addressed in several reviews. However, despite the advantages of l-LA fermentation by Bacillus strains, including its high growth rate, utilization of various carbon sources, tolerance to high temperature, and growth in simple nutritional conditions, it has not been reviewed. This review article discusses new findings on LA-producing Bacillus strains and compares them to other producers. The future prospects for LA-producing Bacillus strains are also discussed.

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A unique autothermal thermophilic aerobic digestion (ATAD) process has been used to convert human excreta to liquid fertilizer in Japan. This study investigated the changes in physicochemical and bacterial community characteristics during the full-scale ATAD process operated for approximately 3 weeks in 2 different years. After initiating simultaneous aeration and mixing using an air-inducing circulator (aerator), the temperature autothermally increased rapidly in the first 1 to 2 days with exhaustive oxygen consumption, leading to a drastic decrease and gradual increase in oxidation-reduction potential in the first 2 days, reached >50°C in the middle 4 to 6 days, and remained steady in the final phase. Volatile fatty acids were rapidly consumed and diminished in the first 2 days, whereas the ammonia nitrogen concentration was relatively stable during the process, despite a gradual pH increase to 9.3. Principal-coordinate analysis of 16S rRNA gene amplicons using next-generation sequencing divided the bacterial community structures into distinct clusters corresponding to three phases, and they were similar in the final phase in both years despite different transitions in the middle phase. The predominant phyla (closest species, dominancy) in the initial, middle, and final phases were (, 19 to 43%; , 6.3 to 30%), (, 43 to 54%), and (, 11 to 28%; , 2.1 to 16%), respectively. Two predominant operational taxonomic units (OTUs) in the final phase showed very low similarities to the closest species, indicating that the process is unique compared with previously published ones. This unique process with three distinctive phases would be caused by the aerator with complete aeration. Although the autothermal thermophilic aerobic digestion (ATAD) process has several advantages, such as a high degradation capacity, a short treatment period, and inactivation of pathogens, one of the factors limiting its broad application is the high electric power consumption for aerators with a full-scale bioreactor. We elucidated the dynamics of the bacterial community structures, as well as the physicochemical characteristics, in the ATAD process with a full-scale bioreactor from human excreta for 3 weeks. Our results indicated that this unique process can be divided into three distinguishable phases by an aerator with complete aeration and showed a possibility of shortening the digestion period to approximately 10 days. This research not only helps to identify which bacteria play significant roles and how the process can be improved and controlled but also demonstrates an efficient ATAD process with less electric power consumption for worldwide application.

BackgroundUrinary tract infection (UTI) is one of the frequently diagnosed infectious diseases which is caused mainly by Escherichia coli. E. coli confers resistance against the two major classes of antibiotics due to the production of extended spectrum β-lactamase enzymes (ESBL), biofilm, etc. Biofilm produced by uropathogenic E. coli (UPEC) protects from host immune system and prevent entry of antimicrobial compounds. The main objective of this cross-sectional study was to determine the correlation of biofilm production and antibiotic resistance as well as to characterize the pgaA and pgaC genes responsible for biofilm formation among uropathogenic ESBL producing E. coli.MethodsA total of 1977 mid-stream urine samples were examined and cultured for bacterial strain identification. ESBL was detected by combined disc method following CLSI whereas biofilm formation was analyzed by semi-quantitative method. Furthermore, the pgaA and pgaC genes responsible for biofilm formation in UPEC were detected by multiplex PCR. All the statistical analyses were done via IBM SPSS Statistics 21 where Pearson’s correlation test were used to determine correlation (−1 ≥ r ≤ 1).ResultsE. coli was the predominant causative agent, which accounted 159 (59.3%) of the Gram-negative bacteria, where 81 (50.9%) E. coli strains were found to be ESBL producers. In addition, 86 (54.1%) E. coli strains were found to be biofilm producers. Both the pgaA and pgaC genes were detected in 45 (93.7%) the UPEC isolates, which were both biofilm and ESBL producers. Moreover, there was a positive correlation between biofilm and ESBL production.ConclusionThe analyses presented weak positive correlation between biofilm and ESBL production in which biofilm producing UPEC harbors both pgaA and pgaC genes responsible for biofilm formation.

A newly isolated Bacillus sp. MC-07 showed 99.2 % 16S rRNA gene sequence similarity with the Bacillus thermoamylovorans LMG 18084(T). It demonstrated optimum and maximum growth temperatures of 50 and 62 °C, respectively. The ability of MC-07 to produce optically pure L-lactic acid via direct fermentation of starch without enzymatic hydrolysis was investigated at different pH values (6.0-8.0) by intermittent adjustments every 12 h. During batch fermentation in mineral salt medium containing 0.001 % yeast extract at pH 7.0, 20 g/L of soluble starch was utilized to produce 16.6 g/L L-lactic acid at 50 °C within 24 h of fermentation, with 100 % optical purity, 92.1 % lactic acid selectivity, and an L-lactic acid yield of 0.977 g/g. Direct starch fermentation at pHs 6.0, 6.5, 7.5, and 8.0 resulted in considerably lower concentrations of lactic acid than did at pH 7.0. Compared with B. thermoamylovorans LMG 18084(T), the ability of strain MC-07 to produce L-lactic acid was superior.

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The emergence of multidrug resistant (MDR) bacteria which is attributable to extended spectrum β-lactamases (ESBLs) production of CTX-M types is an obvious problem worldwide. This study is aimed at determining the prevalence of CTX-M β-lactamases producing multidrug resistant Escherichia coli and Klebsiella pneumoniae among patients attending Bir Hospital. A cross-sectional study was conducted between April and September 2019 at Bir Hospital, Kathmandu, and Department of Microbiology, National College, Kathmandu, Nepal. A total of 5,690 different clinical specimens were subjected to cultural, microscopic, and biochemical analyses for the identification of the isolates. Antimicrobial susceptibility testing of the isolates was done, and MDR isolates were selected and processed for further ESBL confirmation by the combination disks method. All confirmed ESBL isolates were screened for CTX-M type β-lactamases (blaCTX-M) by PCR. Of the total 345 isolates (227 Escherichia coli and 118 Klebsiella pneumoniae), 232 were MDR. All 232 (67.24%) MDR isolates were suspected as ESBL producers on the screening test. However, on the phenotypic test, 135 (58.18%) of total MDR bacteria were confirmed as ESBL producers with the highest proportion in K. pneumoniae (59.37%). The major source of ESBL producers was urine. ESBL producing isolates were mostly identified from outpatients and patients belonging to age group 41-60. Gentamicin was found to be effective against ESBL producers. The prevalence of blaCTX-M was (89.62%) with the highest frequency for E. coli (93.81%). High prevalence of ESBL of CTX-M types among MDR E. coli and K. pneumoniae was detected from clinical specimens of patients in Bir Hospital. This study warrants the need for the judicious use of antibiotics as well as emphasize the use of modern diagnostic tools for the early detection of MDR and ESBL producers to curb the emergence and spread of MDR and ESBL producing bacteria in the clinical settings of Nepal.