Sukanta Kumar Sen

Characterization of Bacilli Isolated from the Gut of Rohu, Labeo rohita, Fingerlings and Its Significance in Digestion

Abstract Three types of intestinal bacteria (Lr 1.1, Lr 1.2, and Lr 2.2) were isolated from the gut of rohu, Labeo rohita, fingerlings. Pure cultures of the bacteria were grown on Tryptone Soya Agar (TSA) plates and were identified as Bacillus circulans, B. pumilus, and B. cereus through morphological, physiological and biochemical tests. The extracellular protease, amylase, and cellulase producing capacity of the isolated organisms were detected in in vitro culture. Biochemical characterization of the isolates suggests that the microorganisms (Bacillus circulans, B. pumilus, and B. cereus) might play an important role in the nutrition of rohu fingerlings. The results of the study will be helpful in formulation of practical diets incorporating non-conventional ingredients.

Duckweed (Lemna polyrhiza) leaf meal as a source of feedstuff in formulated diets for rohu (Labeo rohita Ham.) fingerlings after fermentation with a fish intestinal bacterium

Eight isonitrogenous (35% crude protein approximately) and isocaloric (4.2 kcal g(-1) approximately) diets were formulated including raw and fermented duckweed (Lemna polyrhiza) leaf meal at 10%, 20%, 30% and 40% levels. A particular bacterial strain (Bacillus sp.) isolated from carp (Cyprinus carpio) intestine and having extracellular amylolytic, cellulolytic, proteolytic and lipolytic activities was used for leaf meal fermentation for 15 days at 37 degrees C. The fibre content of leaf meal reduced from 11.0% to 7.5% and the antinutritional factors, tannin and phytic acid, were reduced from 1.0% to 0.02% and 1.23% to 0.09%, respectively after fermentation. However, the available reducing sugars, free amino acids and fatty acids increased in the fermented leaf meal. The response of rohu, Labeo rohita, fingerlings fed the experimental diets for 80 days was compared with fish fed a fish meal based reference diet. On the basis of growth response, food conversion ratio and protein efficiency ratio, 30% fermented Lemna leaf meal incorporated in the diet resulted in the best performance of rohu fingerlings. In general, growth and feed utilization efficiencies of fish fed fermented leaf meal containing diets were superior to those fed diets containing raw leaf meal. The apparent protein digestibility (APD) decreased with increasing levels of leaf meal irrespective of treatment. The APD for raw leaf meal was lower at all levels of inclusion in comparison to those for the fermented meals. The highest carcass protein and lipid deposition was recorded in fish fed the diet containing 30% fermented leaf meal. The results showed that fermented Lemna leaf meal can be incorporated into carp diets up to 30% level compared to 10% level of raw meal.

Production, purification and characterization of a novel thermotolerant endoglucanase (CMCase) from Bacillus strain isolated from cow dung

In an attempt to screen out cellulase producing bacteria from herbivorous animal fecal matter it was possible to isolate a potent bacterium from cow dung. The bacterium was identified as Bacillus sp. using 16S rDNA based molecular phylogenetic approach. The effect of different agricultural wastes, paper wastes and carboxymethyl cellulose on endoglucanase production was tested and was found to produce maximally at 8% carboxymethyl cellulose. The endoglucanase was precipitated by ammonium sulfate saturation and purified by DEAE- Sepharose column. The purification was achieved 8.5 fold from the crude extract with a yield of 68.1%. The molecular weight of the protein was determined to be 97 kDa by SDS-PAGE. The enzymatic activity was moderately reduced by detergents (SDS, Tween-80), metal ions (MnCl2, ZnCl2) and EDTA. The endoglucanase was stable between pH 5.0 – 9.0 and temperature between 20−70°C with optimal activity at pH 7.0 and temperature 50°C. The apparent Km value of the enzyme for the substrate carboxymethyl cellulose was recorded to be 0.25 mg/ml. The endoglucanase was stable in the presence of commercial detergents such as Ariel, Surf Excel and Tide, indicated might be of potential applications in detergent industry. The enzyme from this strain could also be applied in bioconversion of lignocellulosic biomass into fermentable sugars.

Microbial transformation of xenobiotics for environmental bioremediation

The accumulation of recalcitrant xenobiotic compounds is due to continuous efflux from population and industrial inputs that have created a serious impact on the pristine nature of our environment. Apart from this, these compounds are mostly carcinogenic, posing health hazards which persist over a long period of time. Metabolic pathways and specific operon systems have been found in diverse but limited groups of microbes that are responsible for the transformation of xenobiotic compounds. Distinct catabolic genes are either present on mobile genetic elements, such as transposons and plasmids, or the chromosome itself that facilitates horizontal gene transfer and enhances the rapid microbial transformation of toxic xenobiotic compounds. Biotransformation of xenobiotic compounds in natural environment has been studied to understand the microbial ecology, physiology and evolution for their potential in bioremediation. Recent advance in the molecular techniques including DNA fingerprinting, microarrays and metagenomics is being used to augment the transformation of xenobiotic compounds. The present day understandings of aerobic, anaerobic and reductive biotransformation by co-metabolic processes and an overview of latest developments in monitoring the catabolic genes of xenobiotic-degrading bacteria are discussed elaborately in this work. Till date, several reviews have come up, highlighting the problem of xenobiotic pollution, yet a comprehensive understanding of the microbial biodegradation of xenobiotics and its application is in nascent stage. Therefore, this is an attempt to understand the microbial role in biotransformation of xenobiotic compounds in context to the modern day biotechnology.

Distribution of enzyme-producing bacteria in the digestive tracts of some freshwater fish

Background. The information on gut microflora in fish is scanty and there is a paucity of knowledge regarding microbial enzyme activity in fish gastrointestinal tracts. Although some information is available on the enzymeproducing bacteria in fish digestive tracts, almost nothing is known about their distribution in different regions of the gut. In the present study, an attempt has been made to investigate the distribution of enzyme-producing microflora in the foregut and hindgut regions of seven culturable freshwater teleosts. Materials and Methods. Isolation and enumeration of aerobic bacterial flora in the foregut and hindgut regions of the gastrointestinal tracts of seven freshwater teleosts of different feeding habits, namely rohu, Labeo rohita; catla, Catla catla; mrigal, Cirrhinus mrigala; bata, Labeo bata; orange-fin labeo, Labeo calbasu; Nile tilapia, Oreochromis niloticus; and climbing perch, Anabas testudineus, have been carried out. Microbial culture of the gut mucosa on selected nutrient media, following the enrichment culture technique, was done for bacterial isolation. Bacterial isolates were qualitatively screened on the basis of their extracellular enzyme-producing ability. The selected strains were further quantitatively assayed for amylase, cellulase and protease activities. Results. In general, bacterial population was lower in the foregut region of all the seven species of fish examined. Amylolytic strains were present in higher densities in the foregut region of orange-fin labeo and bata (12.20 × 103 CFU · g–1 gut tissue and 11.50 × 103 CFU · g–1 gut tissue, respectively) in comparison to the hindgut region. The cellulolytic population exhibited maximum densities in the hindgut region of bata (7.20 × 103 CFU · g–1 gut tissue) followed by the foregut region of the same fish (5.50 × 103 CFU · g–1 gut tissue). Amylolytic and cellulolytic bacterial flora was not detected in both the fore and hindgut regions of climbing perch. Proteolytic bacterial flora was found in all the species of fish studied and the maximum count was observed in the hindgut region of bata (13.40 × 103 CFU · g–1 gut tissue), orange-fin labeo (9.00 × 103 CFU · g–1 gut tissue), Nile tilapia (8.30 × 103 CFU · g–1 gut tissue) and climbing perch (7.20 × 103 CFU · g–1 gut tissue). Minimum count of proteolytic bacterial flora was observed in the foregut region of all the fishes studied. Peak amylase and cellulase activities were exhibited by bacterial strains isolated from the foregut of orange-fin labeo (266.43 ± 0.15 U) and the hindgut of bata (64.01 ± 0.42 U), respectively. Maximum protease activity was exhibited by a strain isolated from the hindgut region of orange-fin labeo (44.33 ± 0.09 U), followed by the strains isolated from the hindgut regions of climbing perch (32.87 ± 0.12 U), bata (29.71 ± 0.11 U), and Nile tilapia (29.46 ± 0.11 U). Conclusions. The results of the present study indicate that there is a distinct microbial source of digestive enzymes apart from the endogenous sources in fish digestive tracts. The enzyme-producing bacteria isolated from the digestive tracts can be beneficially used as a probiotic while formulating aquafeeds, especially in the larval stages. However, further investigations are required to determine if the addition of such isolates to fish feeds do, in fact, provide some kind of benefit to the fish involved before advocating their use.

Indoor and outdoor aeromycological survey in Burdwan, West Bengal, India

A comparative survey of airborne fungal spores in fiveindoor and five outdoor environments in Burdwan, WestBengal, India, was carried out for a period of twoyears using rotorod samplers and sedimentation plates(culture plate). A total of 29 spore types wereidentified, of which three were Phycomycetous (Mucor, Rhizopus, Syncephalastrum), one Ascomycetous(Chaetomium), one Basidiomycetous (Ganoderma) and the remainder were Fungi Imperfecti. The results revealed lowest count during summer andmaximum during the rainy season. Aspergilluswas quite abundant in all the environments surveyed. The predominance of Aspergillus, Curvularia,Alternaria, Cladosporium, Drechslera, Fusarium in allthe surveyed environments has been attributed to theirability to grow in various substrata. The occurrenceof Cladosporium in the winter months suggestthat it is sensitive to high temperature. Allspore types were common in both environmentsexcept Bispora, Cercospora, Papularia, Spegazzinia, Trichothecium in the outdoor sites. Acorrelation has been made between the volumetriccomposition of airspora and the incidence of seasonalmold allergy.

ANTIBIOTIC PRODUCTION BY STREPTOMYCES HYGROSCOPICUS D1.5: CULTURAL EFFECT

In an attempt to screen out new potent antibiotic producers from soil, Streptomyces hygroscopicus D1.5 was isolated and was found antagonistic to both bacteria and fungi. It could utilise arginine as nitrogen source and glycerol as carbon source at 0.75 g/l and 11.5 g/l level, respectively for maximum antibiotic yield.

Production and partial characterisation of an inducer-dependent novel antifungal compound(s) by Pediococcus acidilactici LAB 5

BACKGROUND Pediococcus acidilactici LAB 5 produces an antifungal compound under in vitro conditions in an inducer-dependent manner. The main objective of the present study was to partially characterise this antifungal compound by UV-visible, IR, (1)H NMR, (13)C NMR and GC/MS analyses and also to assess its potentiality against a number of food spoilage, plant-pathogenic and human-pathogenic fungal species. RESULTS The strain produced a broad-spectrum antifungal compound(s) that was induced by certain constituent factors of MRS and malt extract media. The production was higher in solid culture than in broth culture. The product was found to be a mixture of lactic acid and a compound of molecular mass 83. The minimum inhibitory concentrations (MIC90, 1.32-2.86 g L(-1)) of the active extract were much lower than those of sodium benzoate and calcium propionate. Scanning electron micrographs proved its drastic action on the development of conidial structures. CONCLUSION The chemical analysis indicated a novel compound with fungicidal activity. This compound could be used in fermented foods and feeds to extend their shelf life and also in agricultural crop plants against certain fungal pathogens.

Environmentally benign synthesis and antimicrobial study of novel chalcogenophosphates

We report in this work an environmentally benign zinc mediated synthesis of aryl and benzyl phosphorochalcogenoates in ethanol within a short reaction time. In vitro antimicrobial study along with statistical analysis and seed germination assay were performed. These chalcogenophosphates possess strong antimicrobial activity against the reference strains. The antibacterial activity was determined against four standard strains (Bacilus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa). The antifungal activity was evaluated against one fungal strain Candida albicans.

Purification and characterization of a thermostable α-amylase fromBacillus stearothermophilus

A soil isolate ofBacillus stearothermophilus was found to synthesize thermostable α-amylase. The enzyme was purified to homogeneity by ammonium sulfate fractionation and IECC on DEAE-cellulose column. The purified enzyme was considered to be a monomeric protein with a molar mass of 64 kDa, as determined by SDS-PAGE. The enzyme showed a wide range of pH tolerance and maximum activity at pH 7.0. The temperature tolerance was up to 100 °C with more than 90% catalytic activity: the maximum activity was observed at 50 °C. Divalent metal ions exhibited inhibitory effect on the enzyme activity. However, proteinase inhibitor did not react positively.