Nallusamy Sivakumar

Citric acid production by Koji fermentation using banana peel as a novel substrate

The growing demand for citric acid and the current need for alternative sources have encouraged biotechnologists to search for novel and economical substrates. Koji fermentation was conducted using the peels of banana (Musa acuminata) as an inexpensive substrate for the production of citric acid using Aspergillus niger. Various crucial parameters that affect citric acid production such as moisture content, temperature, pH, inoculum level and incubation time were quantified. Moisture (70%), 28 degrees C temperature, an initial pH 3, 10(8) spores/ml as inoculum and 72h incubation was found to be suitable for maximum citric acid production by A. niger using banana peel as a substrate.

Composition and Antibacterial Activity of the Essential Oils of Four Commercial Grades of Omani Luban, the Oleo‐Gum Resin of Boswellia sacraFlueck.

The essential oil compositions of four botanically certified and commercially available samples of Omani lubans (oleo‐gum resins of Boswellia sacra Flueck.), locally known as Hoojri, Najdi, Shathari, and Shaabi in Jibali Arabic, obtained from plants growing in four different geographic locations of the Dhofar region of Oman, were analyzed by GC‐FID, GC/MS, and 13C‐NMR spectroscopy. The market price of these four grades of lubans differed considerably, according to their color, clump size, and texture. However, this study revealed that Hoojri, the first grade luban, and Shaabi, the fourth grade luban, which greatly differed in their price, closely resembled each other in their essential oil composition, yield, and physicochemical characteristics, except the color and texture. The composition, yield, and specific rotation of the oils of Najdi and Shathari, the second and the third grade lubans, respectively, were different from those of Hoojri and Shaabi, but they both had high limonene contents. Najdi oil was different from the other three oils in terms of its high myrcene content. α‐Pinene was the principal component in all the oils and can be considered as a chemotaxonomical marker that confirms the botanical and geographical source of the resins. All the oils showed pronounced activity against a panel of bacteria, and the trend in their bioactivity and their mode of action are discussed.

Production of polyhydroxybutyrate from wheat bran hydrolysate using Ralstonia eutropha through microbial fermentation.

The increasing global demand for sustainable resources necessitates the complete utilization of feedstock. Wheat bran consists of significant amount of cellulose and hemicellulose which can be used as a renewable resource for production of fermentable sugars. In this study, alkaline pretreated wheat bran was enzymatically hydrolyzed using cellulase of Trichoderma reesei (37 FPU/g) and β - glucosidase of Aspergillus niger (50 CBU/g). Among the nitrogen sources tested, ammonium sulphate was identified as best nitrogen source for the production of polyhydroxybutyrate (PHB). The overall sugar concentration was about 62.91g/L with the corresponding sugar yield of 629.1mg/g wheat bran and the sugars released were mainly composed of glucose (48.35g/L) and xylose (14.56g/L). The PHB producing mutant strain, Ralstonia eutropha NCIMB 11599 grown in wheat bran hydrolysate produced cell density, PHB and yield of 24.5g/L, 62.5%, and 0.319g/g sugar respectively, with a productivity of 0. 0.255g/L/h. Thus, the results suggested that the wheat bran could be a potential alternative feedstock as it does not require any detoxification due to less inhibitory compounds for production of high cell density with significant amount of polyhydroxybutyrate.

Partial Characterization of Bacteriocins produced by Lactobacillus acidophilus and Pediococcus acidilactici

Bacteriocin producing Lactobacillus acidophilus and Pediococcus acidilactici were isolated from milk and meat samples, respectively. An attempt was made to produce bacteriocin in a Dairy Based (DB) medium using these organisms. Higher bacteriocin activity was shown by L. acidophilus in the DB medium. Bacteriocins of both the organisms were effective against food pathogens. The bacteriocins were stable at pH 3 - 9 up to 24 h and active at 100oC. The bacteriocins could be stored at -20oC for at least 45 days, at 4oC for 20 days and at 37oC for 5 days.

Effect of nalidixic acid on the morphology and protein expression of Pseudomonas aeruginosa

OBJECTIVE To determine the effect of nalidixic acid on the morphology and protein expression of Pseudomonas aeruginosa (P. aeruginosa). METHODS Nalidixic acid solution of 1 600 μg/mL was prepared. The minimum inhibitory concentration (MIC) for P. aeruginosa was determined with tube dilution test. The effect of nalidixic acid on the morphology of P. aeruginosa was studied using light microscope and scanning electron microscope. Changes in protein profile were studied using SDS-PAGE. RESULTS The MIC of nalidixic acid was 700 μg/mL against P. aeruginosa. The exposure of P. aeruginosa to different concentrations of nalidixic acid resulted in deformation of most of the growing cells. At the concentration of 600 μg/mL most of the cells turned into elongated and adhere to each other while some of the cells were bulged. The intensity of protein bands were changed when they exposed to nalidixic acid. CONCLUSIONS The present findings suggest that the morphology and protein expression of P. aeruginosa is greatly affected by nalidixic acid.

Antibiofilm Activity of Dendrophthoe falcata against Different Bacterial Pathogens

Dendrophthoe falcata is a hemiparasitic plant commonly used for ailments such as ulcers, asthma, impotence, paralysis, skin diseases, menstrual troubles, pulmonary tuberculosis, and wounds. In this context, the validations of the traditional claim that the leaf extract of D. falcata possesses antibiofilm and anti-quorum sensing activity against different bacterial pathogens were assessed. The bacterial biofilms were quantified by crystal violet staining. Among the 17 bacterial pathogens screened, the methanolic fraction of the leaf extract clearly demonstrated antibiofilm activity for Proteus mirabilis, Vibrio vulnificus, Aeromonas hydrophila, Shigella sonnei, Chromobacterium violaceum ATCC 12472, Vibrio parahaemolyticus, Vibrio harveyi, Vibrio alginolyticus, Vibrio cholerae, and Proteus vulgaris. At biofilm inhibitory concentrations, biofilm formation was reduced by up to 70-90 %. Furthermore, the potential quorum-sensing activity of the leaf extract was tested by agar well diffusion using Chromobacterium violaceum (ATCC 12472 & CV O26) reporter strains. The inhibition of violacein production may be due to direct or indirect interference on QS by active constituents or the interactive effect of different phytocompounds present in the extracts. This is the first report on antibiofilm and QS activity of D. falcata leaf extracts, signifying the scope for development of complementary medicine for biofilm-associated infections.

Fish Waste-Potential Low Cost Substrate for Bacterial Protease Production: A Brief Review

Industrial biotechnology processes have recently been exploited for an economic utilization of wastes to produce value added products. Of which, fish waste is one of the rich sources of proteins that can be utilized as low cost substrates for microbial enzyme production. Fish heads, tails, fins, viscera and the chitinous materials make up the wastes from fish industries. Processing these wastes for the production of commercial value added products could result in a decrease in the cost of production. In addition, we can eliminate the pollution of the environment and health issues due to the improper disposal of these fish wastes. This review highlights the potential use of fish waste as a cheaper substrate for the production of economically important protease enzyme.

Isolation and characterization of cellulolytic Bacillus licheniformis from compost

Eight cellulose degrading bacteria were isolated from compost and were identified as Bacillus licheniformis by 16S rRNA sequencing. Among the eight isolates, Bacillus licheniformis B4, B7 and B8 showed the highest cellulase activity. B. licheniformis B4 and B8 showed the maximum cellulase activity during the stationary phase of growth; but for B7, the maximum activity of cellulase was observed during the log phase. Reducing sugar released in the media, increased with increasing cellulase activity for all the three isolates. Significant correlation was observed between cellulase activity and protein content. The crude cellulase from B7 strain showed activity towards carboxymethyl cellulose and filter paper, but there was no detectable activity towards p-nitrophenyl- β-Dglucopyranoside (PNPG). The crude cellulase of B. licheniformis B7 exhibited maximum activity at 50°C and at pH 6 to 7. Keywords: Bacillus licheniformis , 16S rRNA, cellulase, reducing sugar, compost, viscosity

Cellobiohydrolases: Role, Mechanism, and Recent Developments

Cellobiohydrolases or exoglucanases are produced by various bacteria and fungi with catalytic modules belonging to families 5, 6, 7, 9, 48, and 74 glycoside hydrolases, which act at the chains end of cellulose resulting in release of glucose as well as cellobiose. The CBH I and II works processively from reducing and nonreducing ends of the cellulose chain, respectively. The catalytic module of CBHs is the tunnel structure formed by two surface loops that may covers entirety or part of active site evidenced that the mode of action proceeds in a processive manner as cellobiohydrolase progresses along the cellulose chain. CBHs are able to work actively in the crystalline region of cellulose, probably peeling them from the microcrystalline structure of Avicel. Although several assays have been proposed, no specific substrate as well as assay method to measure exoglucanases has been described till date. In recent days, several new approaches such as δ-sequence mediated integration, SCHEMA, and FoldX and a ‘consensus’ sequence have been developed to improve activity and stability of CBHs.

Waste office paper: A potential feedstock for cellulase production by a novel strain Bacillus velezensis ASN1

This paper reports the cellulase (FPase) production by newly isolated Bacillus velezensis ASN1 using waste office paper (WOP) as feedstock and optimization of production conditions through two level factorial design, steepest ascent/descent and second order response surface methodology (RSM). Various fermentation parameters, like chemical factors (potassium dihydrogen phosphate, potassium chloride, yeast extract, magnesium sulphate, sodium nitrate, Tween 80, and waste office paper), physical factors (temperature, pH and time) and biological factor (inoculum size) were examined using two level full factorial design to check the key factors significantly affecting the cellulase production. The central composite design (CCD) was used to optimize the vital fermentation parameters, such as carbon (WOP), nitrogen, pH, and inoculum concentration in the medium for achieving higher cellulase production. The optimum medium composition was found to be WOP (9 g/L), sodium nitrate (0.35 g/L), inoculum size (6.56%) and pH 4.72. The model prediction of 2.46 U/mL cellulase activity at optimum conditions was verified experimentally as 2.42 U/mL.