Chiranjit Maity

Production of cellulolytic enzymes by Aspergillus fumigatus ABK9 in wheat bran-rice straw mixed substrate and use of cocktail enzymes for deinking of waste office paper pulp.

Response surface methodology was employed to optimize mixed substrate solid state fermentation for the production of cellulases and xylanase by Aspergillus fumigatus ABK9. Among 11 different parameters, fermentation time (86-88 h), medium pH (6.1-6.2), substrate amount (10.0-10.5 g) and substrate ratio (wheat bran:rice straw) (1.1) had significantly influences on enzyme production. Under these conditions endoglucanase, β-glucosidase, FPase (filter paper degrading activity) and xylanase activities of 826.2, 255.16, 102.5 and 1130.4 U/g, respectively were obtained. The enzyme cocktail extracted (solid to water ratio of 1:10) from the ferments increased brightness of waste office paper pulp by 82.8% ISO, Ink(D) value by 82.1%, removed chromophores (2.53 OD; A(237)nm) and hydrophobic compounds (1.15 OD; A(465)nm) and also decreased the kappa number to 13.5 from 16.8.

Alteration of predominant gastrointestinal flora and oxidative damage of large intestine under simulated hypobaric hypoxia.

Hypobaric hypoxia is an immediate and crucial starting mechanism of acute mountain sickness included with some non-specific gastrointestinal (GI) complications. To study the effect of hypoxia on GI microflora and its upshot to this system, male albino rats were exposed to 55 kPa (air pressure ~ 4872.9 m altitude) consecutively 30 days for 8 hours/day. The different indicator group of large intestinal microbial populations were enumerated and correlated with the levels of antioxidant indicators like catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), reduced glutathione (GSH) and oxidized glutathione (GSSG) of large intestinal epithelial cells. In addition, the histological study was performed by haematoxylin eosin (HE), periodic acid schiff staining (PAS) and scanning electron microscopy (SEM). It was observed that the density of total aerobes (104 folds) significantly (p < 0.05) decreased but the population of total anaerobes (209 folds) and Escherichia coli (125 folds) elevated after 30 days of hypoxic stress. The strict anaerobes like Bifidobacterium spp. (3 folds), Bacteroides spp. (134 folds), Lactobacillus spp. (7 folds) and other selected obligate anaerobes like Clostridium perfringens (40 folds), Peptostreptococcus spp. (21 folds) increased in respect to their control population. The growth direction index (GDI) of anaerobic populations was positive and correlated with gas formation aptitude. The activities of CAT and SOD in the large intestinal epithelia decreased significantly (p < 0.05) and GSH/GSSG pool turned into oxidized state with higher MDA (p < 0.05) formation. Histological study revealed the necrotized epithelial layer with higher lymphocytes infiltration in lamina propia accompanied by reduction of acidic mucins secreting goblet cells. From this experiment, it can be hypothesized that high altitude induced hypoxia manipulated the bacterial imprint and damaged the epithelial barrier of the large intestine which may cause systemic infection.

Tannase Production by Penicillium purpurogenum PAF6 in Solid State Fermentation of Tannin-Rich Plant Residues Following OVAT and RSM

Tannase production by newly isolated Penicillium purpurogenum PAF6 was investigated by ‘one variable at a time’ (OVAT) approach followed by response surface methodology (RSM). Tannin-rich plant residues were used as supporting solid substrate and sole carbon source and, among them, tamarind seed was found to be the most favorable substrate than haritaki, pomegranate, tea leaf waste and arjun fruit. Physicochemical parameters were initially optimized using OVAT methodology and some important factors like incubation time, incubation temperature, substrate:moisture ratio as well as carbon, nitrogen and phosphate concentrations were verified with Box–Behken design of response surface methodology. Phosphate source, nitrogen source and temperature were found as the most favorable variables in the maximization of production. Tannase production was enhanced from 1.536 U/g to 5.784 U/g using tamarind seed OVAT optimization and further enhancement up to 6.15 U/g following RSM. An overall 3.76- and 4.0-fold increases in tannase production were achieved in OVAT and RSM, respectively.

The potential of immobilized bacterial α-amylase on coconut coir, a smart carrier for biocatalysts

Purified α-amylase from a soil bacterium Bacillus sp. SKB4 was immobilized on coconut coir, an inexpensive cellulosic fiber, with the cross-linking agent glutaraldehyde. The catalytic properties and stability of the immobilized enzyme were compared with those of its soluble form. The enzyme retained 97.2% of its activity and its catalytic properties were not drastically altered after immobilization. The pH optimum and stability of the immobilized enzyme were shifted towards the alkaline range compared to the free enzyme. The optimum temperature for enzymatic activity was 90°C in both forms of the enzyme. The soluble and immobilized enzyme retained 19% and 70% of original activity, respectively, after pre-incubation for 1 h at 90°C. Immobilized amylase was less susceptible to attack by heavy metal ions and showed higher Km and Vmax values than its free form. The bound enzyme showed significant activity and stability after 6 months of storage at 4°C. All of these characteristics make the new carrier system suitable for use in the bioprocess and food industries.

Purification and characterization of an endoxylanase from the culture broth of Bacillus cereus BSA1

An extracellular xylanase from the fermented broth of Bacillus cereus BSA1 was purified and characterized. The enzyme was purified to 3.43 fold through ammonium sulphate precipitation, DEAE cellulose chromatography and followed by gel filtration through Sephadex-G-100 column. The molecular mass of the purified xylanse was about 33 kDa. The enzyme was an endoxylanase as it initially degraded xylan to xylooligomers. The purified enzyme showed optimum activity at 55°C and at pH 7.0 and remained reasonably stable in a wide range of pH (5.0–8.0) and temperature (40–65°C). The Km and Vmax values were found to be 8.2 mg/ml and 181.8 μmol/(min mg), respectively. The enzyme had no apparent requirement of cofactors, and its activity was strongly inhibited by Cu2+, Hg2+. It was also a salt tolerant enzyme and stable upto 2.5 M of NaCl and retained its 85% activity at 3.0 M. For stability and substrate binding, the enzyme needed hydrophobic interaction that revealed when most surfactants inhibited xylanase activity. Since the enzyme was active over wide range of pH, temperature and remained active in higher salt concentration, it could find potential uses in biobleaching process in paper industries.

Regulation of Xylanase Biosynthesis in Bacillus cereus BSA1

Microbial xylanases have a promising biotechnological potential to be used in industries. In this study, regulation of xylanase production was examined in Bacillus cereus BSA1. Xylanase production was induced by xylan. The enzyme production further increased in the presence of xylose and arabinose in very low concentration with addition of xylan (0.5% up to 6.02 U/ml). Addition of glucose (about 0.1%) to the media supplemented with xylan repressed xylanase production. Even higher concentration (>0.1%) of xylose and arabinose repressed xylanase biosynthesis. Glucose-mediated repression was partially relived by addition of cyclic adenosine monophosphate. Chemical like 2-4-dinitrophenol, which can inhibit adenosine triphosphate synthesis in cell, repressed xylanase synthesis and it suggested xylanase synthesis to be an energy dependent process.

Thermodynamics and kinetic properties of halostable endoglucanase from Aspergillus fumigatus ABK9

An endoglucanase from Aspergillus fumigatus ABK9 was purified from the culture extract of solid‐state fermentation and its some characteristics were evaluated. The molecular weight of the purified enzyme (56.3 kDa) was determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, zymogram analysis and confirmed by MALDI‐TOF mass spectrometry. The enzyme was active optimally at 50 °C, pH 5.0 and stable over a broad range of pH (4.0–7.0) and NaCl concentration of 0–3.0 M. The pKa1 and pKa2 of the ionizable groups of the active sites were 2.94 and 6.53, respectively. The apparent Km, Vmax, and Kcat values for carboxymethyl cellulose were 6.7 mg ml−1, 775.4 µmol min−1, and 42.84 × 104 s−1, respectively. Thermostability of the enzyme was evidenced by the high activation energy (91.45 kJ mol−1), large enthalpy for activation of denaturation (88.77 kJ mol−1), longer half‐life (T1/2) (433 min at 50 °C), higher melting temperature (Tm) (73.5 °C), and Q10 (1.3) values. All the characteristics favors its suitability as halotolerant and thermostable enzyme during bioprocessing of lignocellulosic materials.

Study of the cultivable microflora of the large intestine of the rat under varied environmental hyperbaric pressures

BACKGROUND/PURPOSE(S) We conducted an in vivo experiment to investigate the effect of hyperbarometric air pressure on the quantity and composition of the cultivable microflora of the large intestine. METHODS Using selective culture-based methods, we enumerated from the large intestine total aerobes and total anaerobes, and indicator bacteria such as Escherichia coli, other Enterobacteriaceae, Bifidobacterium spp., Lactobacillus spp. and Clostridium perfringens, and studied their quantitative variation. RESULTS Total aerobes and facultative anaerobes (E. coli and other Enterobacteriaceae) were increased with an increase in air pressure, whereas the increase caused a drastic reduction in the numbers of total anaerobes and Clostridium perfringens. Bifidobacterium spp. and Lactobacillus spp. were affected slightly by the altered air pressures. Variation in the numbers of these groups of bacteria was correlated to dose and duration of hyperbaric treatment. CONCLUSION We conclude from our results that air pressure is an important exogenous factor that strongly modulates bacterial colonization of the large intestine and the composition of the intestinal microflora, and that the occurrence of gastrointestinal disorders during hyperbarism is a result of alteration in the indigenous microflora.

Effect of graded hyperbaric atmospheric pressure on the quantity and composition of faecal flora

Objectives: The ecosystem of the intestinal flora is always dynamic and it is maintained even in the changing chemical and physical environment of the host. The effects of the physical environment such as atmospheric pressure on the composition of intestinal flora has not been studied previously. Considering this, an in vitro experiment was designed to explore the effects of hyperbaromatric pressure on the faecal flora of the rat. Materials and methods: Faecal samples from male albino rat were exposed to graded hyperbaric conditions (122 and 170 kilopascal, kPa) for different time periods (1, 3 and 5 h). Total aerobes, total anaerobes, Escherichia coli, Bifidobacterium spp. and Clostridium perfringens present in the faecal samples were quantified by specific culture-based methods. Variation in their number in comparison to control conditions was analysed statistically (ANOVA and Tukey t test). Results: The numbers of total aerobes and E. coli were increased with the increase in air pressure, whereas a reduction in numbers was recorded for total anaerobes, Bifidobacterium spp. and C. perfringens. Variations of these groups of bacteria in relation to dose and duration of hyperbaric treatment were also recorded. Conclusion: Air pressure is an important exogenous factor that strongly regulates the composition of the faecal flora.

Investigating the effect of storage temperature and hot-water treatment on the microbial dynamics in edible oyster (Saccostrea cucullata)

Oysters are an important sea food all over the world apart from shrimp and crabs. They are usually sold as a live product and can be stored for several weeks before consumption. Temperature abuse during oyster post-harvest handling may allow multiplication of natural spoilage microflora as well as pathogens, which is a potential threat to consumers and/or compromising product quality. In this study, the effect of storage temperatures (25°C, 4°C, 0°C and –10°C) and boiling on the microbial quality of shell stock and shucked meats of oysters (Saccostrea cucullata) were examined. The load of total bacteria, fungi, coliform, fecal coliform, Salmonella sp. and Streptococcus sp. were comparatively higher in shucked meat than in the shell-stock at all the storage temperatures (except Vibrio sp.) and the number of the spoilage bacteria is directly proportional to the storage time but decreased with lowering of the temperature. Microbial count also observed at various interval of treatment with boiling water (100°C). During boiling water treatment of the shell-stock and shucked meats, the decimal reduction time, D-value (D100°C) for total microbes was found to be 2.7 min and 2.4 min respectively. The results indicated that oysters must be stored for a limited time as shell-stock and during cooking it should be prepared as shucked meats, and washing with boiled water is a simple method for making it microbes free.