Rintu Banerjee

Enzymatic transesterification of Jatropha oil

BackgroundTransesterification of Jatropha oil was carried out in t-butanol solvent using immobilized lipase from Enterobacter aerogenes. The presence of t-butanol significantly reduced the negative effects caused by both methanol and glycerol. The effects of various reaction parameters on transesterification of Jatropha oil were studied.ResultsThe maximum yield of biodiesel was 94% (of which 68% conversion was achieved with respect to methyl oleate) with an oil:methanol molar ratio of 1:4, 50 U of immobilized lipase/g of oil, and a t-butanol:oil volume ratio of 0.8:1 at 55°C after 48 h of reaction time. There was negligible loss in lipase activity even after repeated use for seven cycles.ConclusionTo the best of our knowledge this is the first report on biodiesel synthesis using immobilized E. aerogenes lipase.

Enhanced production of amylase by optimization of nutritional constituents using response surface methodology

Abstract Response surface methodology was employed to study the cumulative interactive effect of the macronutrients of the media and to optimize their concentration to enhance the production of maltooligosaccharide-forming amylase from Bacillus circulans GRS 313. A 23 factorial central composite experimental design was used to study the combined effect of the nutritional constituents like soybean meal, yeast extract and wheat bran. The p-value of the coefficient for linear effect of soybean meal concentration was found to be 0.081, suggesting that this was the principal experimental variable having the greatest effect on the production of maltooligosaccharide-forming amylase. The optimal combination of the media constituents for amylase production from the contour plots were: soybean meal =4.84 g /100 ml , yeast extract =1.58 g /100 ml , wheat bran =2.84 g /100 ml . The optimization of the media increased the amylase yield by 1.25 times.

Microbial production of gallic acid by modified solid state fermentation

Bioconversion of tannin to gallic acid from powder of teri pod (Caesalpinia digyna) cover was achieved by the locally isolated fungus, Rhizopus oryzae, in a bioreactor with a perforated float for carrying solid substrate and induced inoculum. Modified Czapek-Dox medium, put beneath the perforated float, with 2% tannic acid at pH 4.5, temperature 32°C, 93% relative humidity, incubated for 3 days with 3-day-old inoculum was optimum for the synthesis of tannase vis-à-vis gallic acid production. Conversion of tannin to gallic acid was 90.9%. Diethyl ether was used as the solvent for extraction of gallic acid from the fermented biomass.

Optimization of tannase biosynthesis by a newly isolated Rhizopus oryzae

A strain isolated locally and identified as Rhizopus oryzae (RO, IIT KGP) was found to synthesise an extracellular enzyme, tanin acyl hydrolase, showing its degradability of tannic acid to gallic acid. For maximizing the enzyme secretion in the fermented broth, the influencing parameters were optimized in shake flask culture. Experiments showed that modified Czapek dox medium with 2% tannic acid, 1% glucose, 0.05% sodium nitrate incubated for 4 days with 2 days old inoculum was the optimum for the synthesis of tannase by Rhizopus oryzae (RO, IIT KGP). Maximum enzyme activity was found to be 6.12 U/ml.

Immobilization of alpha-amylase produced by Bacillus circulans GRS 313

A maltooligosaccharide-forming amylase from B circulans GRS 313 was immobilized by entrapment in calcium alginate beads. The immobilized activity was affected by the size of the bead and bead size of 2mm was found to be most effective for hydrolysis. Kinetics constants, Km and Vmax were estimated and were found to be affected by the bead size. The catalytic activity of the enzyme was studied in presence of various starchy residues and metal ions. HgCl2, CuSO4 and FeCl3 caused inhibition of the enzyme. The reaction conditions, pH and temperature, was optimized using response surface methodology. At the optimum pH and temperature of 4.9 and 57oC, the apparent activity was 25.6U/g of beads, resulting in almost 2-fold increase in activity. The immobilized enzyme showed a high operational stability by retaining almost 85% of the initial activity after seventh use.

Seed birth to death: dual functions of reactive oxygen species in seed physiology

BACKGROUND Reactive oxygen species (ROS) are considered to be detrimental to seed viability. However, recent studies have demonstrated that ROS have key roles in seed germination particularly in the release of seed dormancy and embryogenesis, as well as in protection from pathogens. SCOPE This review considers the functions of ROS in seed physiology. ROS are present in all cells and at all phases of the seed life cycle. ROS accumulation is important in breaking seed dormancy, and stimulating seed germination and protection from pathogens. However, excessive ROS accumulation can be detrimental. Therefore, knowledge of the mechanisms by which ROS influence seed physiology will provide insights that may not only allow the development of seed quality markers but also help us understand how dormancy can be broken in several recalcitrant species. CONCLUSIONS Reactive oxygen species have a dual role in seed physiology. Understanding the relative importance of beneficial and detrimental effects of ROS provides great scope for the improvement and maintenance of seed vigour and quality, factors that may ultimately increase crop yields.

Optimization of laccase production using response surface methodology coupled with differential evolution

In the present study, laccase production from a locally isolated hyperactive strain of Pleurotus sp. under solid state fermentation (SSF) was carried out and the interactions between different parameters of fermentation were studied using response surface methodology. The saddle shaped response surface plots depicting dual conditions for the enhanced production indicated the presence of isozymes with production optima at different conditions which was verified experimentally. Isoelectric focusing of the enzyme extract revealed that two isoforms were found with a widely varying pI of 3.8 and 9.3 emphasizing the capacity of the enzyme to be deployed at both acidic and alkaline conditions. Optimization of production conditions by coupling the regression equation with differential evolution technique yielded over 54,600IU/gds (3,412,500U/L) with a surfactant concentration of 0.016%, pH 7.99, particle size of 0.25cm, liquid to solid ratio of 4.99 and an incubation period of 8 days. In this study, the optimization process yielded highest titer value of laccase reported to date.

Effect of additives on the behavioural properties of tannin acyl hydrolase

Abstract The effect of metal ions on tannase activity was studied. One mM Mg +2 or Hg + activated tannase activity. Ba +2 , Ca +2 , Zn +2 , Hg +2 and Ag + inhibited tannase activity at 1.0 mM concentration and Fe +3 and Co +2 completely inhibited tannase activity. Ag + , Ba +2 , Zn +2 and Hg +2 competitively inhibited tannase activity. Among the anions studied 1 mM Br − or S 2 O 3 −2 enhanced tannase activity. Tween 40 and Tween 80 enhanced tannase activity whereas Tween 60 inhibited tannase activity. Sodium lauryl sulfate and Triton X-100 inhibited tannase activity. Urea stimulated tannase activity at a concentration of 1.5 M. Among the chelators chosen for the present study, 1 mM EDTA or 1,10- o -phenanthrolein inhibited tannase activity Dimethyl sulphoxide and β-mercaptoethanol inhibited tannase activity at 1 mM concentration whereas soybean extract inhibited tannase activity at concentrations varying from 0.05 to 1.0% (w/v). Among the nitrogen sources selected ammonium ferrous sulfate, ammonium sulfate, ammonium nitrate and ammonium chloride enhanced tannase activity at 0.1% (w/v) concentration.

Optimization of n variable biological experiments by evolutionary operation-factorial design technique

Since the traditional approach to optimization of biological systems based on the single variable search technique is incapable of detecting the true optimum when a number of chemicals are used together as inducers, the Evolutionary Operation (EVOP)-factorial design technique was applied successfully to optimize the concentrations of vitamin (biotin), metal ion (CaCl(2)) and plant hormone (NAA) for maximizing enzyme (protease) production by Rhizopus oryzae (RO IIT RB-13, NRRL-21498) in solid state fermentation. Addition of inducers to an optimal level (biotin-2.5 ppm, CaCl(2)-20 ppm and NAA-12.5 ppm) resulted in a approximately 1.9-fold increase in protease production.

Production of tannase by solid-state fermentation

An attempt has been made to optimize the production of enzyme tannase by solid state fermentation (SSF) using the organism Rhizopus oryzae. The best favourable conditions for enzyme production include initial pH 5 with 4 days of incubation period at 40°C and 72% humidity, and 10 g wheat bran soaked in 2.5% tannic acid.