The scarcity of hygienic drinking water is a normal phenomenon in the coastal areas of Bangladesh due to the high salinity of ground water. The inhabitants of this locality, therefore, live on alternative supplies of water including rain-fed pond water, and rainwater with persistent complex microbial interactions therein, often contaminated with life-threatening pathogens. Hence, this study was aimed at analyzing the prevalence of Vibrio cholerae (Vc) in the alternative drinking waters of Mathbaria, a coastal subdistrict neighboring the Bay of Bengal, the efficacy of pond sand filter (PSF) and the co-association among Bacillus-like spore formers (Sf) and Vc. Vc presumably entrapped into the membrane filter was enriched in alkaline peptone water medium and was isolated on selective thiosulfate-citrate-bile salts-sucrose and taurocholate-tellurite-gelatin agar media. They were finally identified by immunochromatographic one step rapid test and serology test. A total of 26% Vc positive samples were obtained out of 100 [ponds—48, household (HH)—29, and PSFs—23] where 13% cases were pathogenic (Vc O1) and 13% were non-pathogenic (Vc non-O1/non-O139). The distribution of Vc as observed was 33, 26, and 13.8% in waters derived from pond surface, PSF, and HH reservoirs, respectively, and for pathogenic type, it was 62.5%, 50%, and nil, respectively. Although none of the samples was identified with pathogenic Vc O139, the statistics represents a significant and augmentative risk of cholera outbreak in the focused area. The antibiotic sensitivity pattern in this study resembled the trend observed during last few years for Vc. The PSF demonstrated its inability to remove Vc from any of the samples and in addition, the filter itself was evidenced to be the source of pathogens and spores in further contamination and transmission. The development of biofilm in the PSF could be hypothesized as the reservoir in contaminating pathogen-free water samples. From the test of homogeneity, the risk levels of alternative water sources were estimated equal regarding Vc. Simultaneously, it was determined statistically that the prevalence of Vc, by no means, is influenced by Bacillus-like Sf be it for pond surface, HH, or PSF derived water.

Background. Due to certain limitations, the bioprocess development for protease production needs more convenient and realistic statistical approach instead of conventional optimization technique. For an economic bioprocess with enhanced protease yield, Response Surface Methodology (RSM) based on Central Composite Design (CCD) was employed and evaluated in this study. Materials and methods. The fermentation was performed with a mutant strain, Bacillus licheniformis MZK05M9 (BlM9) using molasses, urea and CaCl 2 .2H 2 O as carbon, nitrogen and trace element sources respectively in shake flask. The conditions for fermentation were maintained with temperature, pH and agitation at 37°C, 7.5 and 150 rpm respectively. The required number of trials were determined by investigating each variable (Molasses, Urea and CaCl 2 ) at five levels: -α, -1, 0, +1 and +α through CCD with protease yield as the response function and the interaction effects as well as optimal parameters were obtained by using Minitab software. The significance of the independent variables and their interactions were tested by means of analysis of variance (ANOVA) with a 95% confidence level and 3-D surface plots were developed through RSM. Results. Upon 20 trials, the optimum values of the tested variables for maximum alkaline protease production as predicted through CCD and RSM were as 0.63%, 0.16%, and 0.11% (w/v) for Molasses, Urea and CaCl 2 .2H 2 O, respectively. The protease activity in Conventionally Optimized (CO) medium was 410 U/ ml and it was predicted as 463.1 U/ ml for statistically optimized medium. Upon experiments with the optimized medium, the protease activity was estimated as 560 U/ ml which was 36.6% (i.e. 1.36 fold) higher than that of CO medium. Conclusion. The efficiency of the enzyme in solubilizing the whole feathers was also assessed which indicated that the enzyme produced with cheap substrates could be utilized as a cost effective and eco-friendly agent in poultry feed formulation, leather processing etc.

Background. The present study was aimed to isolate phytase producing bacteria and optimize the physicochemical parameters of their phytase production. Materials and methods. Four bacterial isolates (Phs4, Phs5, Phs6, and Phs8), based on clear zone formation on phytase screening medium, were selected and tested for finding out the highest phytase producing strain. The production of phytase was then optimized and its biochemical properties were determined to judge the applicability of phytase as a digestive aid in animal feed. Results. The 4 bacterial isolates (Phs4, Phs5, Phs6 and Phs8) were identified by morphological, cultural, biochemical and molecular characterization as Burkholderia cepacia, Escherichia coli, Klebsiella pneumoniae and Klebsiella sp. respectively. Of these isolates, Phs8 (Klebsiella sp.) was found to produce maximum phytase in shake culture in a basal medium containing Na-phytate at 37 o C and pH 5.5 after 72 hours of incubation. The omission of Na-phytate from the medium almost completely abolished the phytase production capacity of the isolate and thus signified its important role as an inducer. Among the different complex carbon sources, viz., glucose, wheat bran, rice bran and chickpea, maximum phytase production (94 unit/ ml) was obtained with wheat bran under comparable cultivation conditions. The phytase works best at a temperature of 37 o C and pH of 4.0 with a wide temperature stability (more than 80% activity up to 80 o C) and wide pH stability (more than 80% activity within a range of pH 3-8). Although Zn 2+ , Co 2+ , and Fe 2+ slightly increased the phytase activity Cu 2+ and Mg 2+ strongly inhibited the enzyme. Conclusion. The present findings will be very useful for the development of a bioprocess of the enzyme for its large-scale production at the pilot and finally at the commercial level.

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