Veeranki Venkata Dasu

Purification and characterization of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428

An intracellular glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428 was isolated to apparent homogeneity. The homotetramer enzyme has a molecular mass of 144.4 kDa (MALDI-TOF MS) and an isoelectric point of approximately 8.4. The enzyme is very specific for its natural substrate, L-asparagine. The activity of L-asparaginase is activated by mono cations and various effectors including Na+, K+, L-cystine, L-histidine, glutathione and 2-mercaptoethanol whereas it is moderately inhibited by various divalent cations and thiol group blocking reagents. Kinetic parameters, Km, Vmax and kcat of purified L-asparaginase from P. carotovorum MTCC 1428 were found to be 0.657 mM, 4.45 U μg(-1) and 2.751×10(3) s(-1), respectively. Optimum pH of purified L-asparaginase for the hydrolysis of L-asparagine was in the range of 8.0-10.0, and its optimum temperature was found to be 40 °C. The purified L-asparaginase has no partial glutaminase activity, which can reduce the possibility of side effects during the course of anti-cancer therapy.

Determination of significant parameters for improved griseofulvin production in a batch bioreactor by Taguchi's method

Abstract Taguchis method was applied to evaluate the significant parameters for griseofulvin production by Penicillium griseofulvum MTCC 1898 in a batch bioreactor. Physical parameter, viz., controlled pH, agitation and aeration had a significant influence on griseofulvin production when compared with chemical parameters and were considered as significant ones.

Optimization of microbiological parameters for enhanced griseofulvin production using response surface methodology

Abstract Central composite design was used to determine the optimal levels of microbiological parameters, viz., slant age, seed age and inoculum level, for enhanced griseofulvin production by Penicillium griseofulvum MTCC 1898 and Penicillium griseofulvum MTCC 2004 in shake flask fermentation. The optimal levels of slant age, seed age and inoculum level for Penicillium griseofulvum MTCC 1898 were found to be 8.8772 days, 4.2093 days, 12% (v/v) (≡17.56 kg dry cell mass/m3) and for Penicillium griseofulvum MTCC 2004, 8.221 days, 3.4875 days and 9% (v/v) (≡8.09 kg dry cell mass/m3) respectively. The yield of griseofulvin under optimal conditions was found to be 1.65 times for Penicillium griseofulvum MTCC 1898 and 1.07 times for Penicillium griseofulvum MTCC 2004 higher than that obtained using unoptimized conditions. The fermentation time for maximum production of griseofulvin by Penicillium griseofulvum MTCC 1898 and Penicillium griseofulvum MTCC 2004 decreased by 4 days and 2 days respectively.

Production and Properties of a Biosurfactant Applied to Polycyclic Aromatic Hydrocarbon Solubilization

Microorganisms isolated from a soil sample collected from a gasoline filling station (located in Guwahati) were tested for their pyrene- and anthracene-degrading potential. Preliminary studies showed the ability of the organism to grow on carbon-free mineral medium (CFMM) supplemented with pyrene as the sole source of carbon. The organisms were found to produce a bioemulsifier when grown on CFMM with glucose or glycerol and/or pyrene as the carbon source. The organisms could also utilize anthracene when grown on mineral salt medium along with 2% glycerol. Within 2 d, anthracene concentration dropped less than 30% of the original concentration. Approximately 100 mg of the emulsifier was isolated from 25 mL of the 5-d-grown culture. The emulsifier was tested to produce emulsion with both an aliphatic and an aromatic group of hydrocarbons and resulting emulsions were found to be stable for a long period of time when keptat 10–15°C. The emulsifier was also quite stable in a pH range of 3.0–11.0. In a concentration range of 0.5–10 mg/mL, it resulted in a linear increment of apparent pyrene and anthracene solubility in water.

Understanding the Complexity and Strategic Evolution in PAH Remediation Research

The development and improvement of society through industrialization and urbanization comes with the cost of consistent deterioration and degradation of the natural environment through generation of toxic and hazardous pollutants. Polycyclic aromatic compounds (PAHs) are a major class of such persistent organic pollutants, posing serous threat to terrestrial and aquatic ecosystems due to their intrinsic low aqueous solubility, higher binding affinity toward soil organic matters, and higher chemical stability, making them less susceptible toward remediation process. Two key issues are covered in the review. First, the severity of contamination and its implications are addressed with reference to source, distribution, and toxicity of PAHs. Second, a detailed overview on significant and systematic changes that have ever been observed in remediation methodology of PAH contaminants in past decades is presented. The remediation and treatment time, contaminant composition and load, site characteristics, and desired degree of cleanup are the decisive factors guiding selection of proper in situ or ex situ remediation technology. It has generally been observed chemical oxidation is the method of choice for rapid reduction (within minutes to couple of hours) of recalcitrant PAHs (e.g., benzo[a]pyrene) load in a more heterogeneous system (e.g., soil) with an efficiency from ∼10% to 100%. On the other hand phytoremediation can effectively handle 3- and 4-ring PAHs (phenanthrene, pyrene) in aged and spiked contaminated soil and sediment system with a similar degree of conversion, but in a long or extended period of time (a couple of months to years). The times scale for ex situ microbial remediation systems in liquid phase are in days to weeks and contaminant load that can effectively be treated varies with the nature and concentration of additives (e.g., surfactants, solvents). Finally, the authors offer general insight about biological treatment methods, with a wider focus into the recent developments in the process.

SYNCHRONOUS FLUORESCENCE AS A SELECTIVE METHOD FOR MONITORING PYRENE IN BIODEGRADATION STUDIES

A simple and effective method based on synchronous fluorescence spectroscopy for quantifying pyrene and its metabolites in a biodegradation study using Mycobacterium frederiksbergense is reported in this work. An optimum excitation-emission wavelength offset of 39 nm and a corresponding excitation wavelength of 335 nm was found to be suitable for the determination of pyrene. Interference due to naphthalene and anthracene in the analysis were found to be 11 and 4.7%, respectively. Batch biodegradation experiments in a 3L fermentor revealed a high pyrene degradation rate of 10.22 mg L− 1 d− 1 by the mycobacterium in presence of the surfactant tween 20. Tween 20 was, however, found preferentially utilized over pyrene, which resulted in a lag of 120 h in pyrene degradation by the culture. In the absence of the surfactant, pyrene degradation rate was found to be only 6.1 mg L− 1 d− 1, but without any lag in its degradation.

Propionic acid production by whole cells of Propionibacterium freudenreichii

Abstract The microbial production of propionic acid by Propionibacterium freudenreichii NCIM 2111, has been studied in this communication. Shake-flask studies were carried out to determine the optimum combination of various process parameters like stab age, inoculum age, inoculum level, medium constituents, temperature, and the initial pH for maximizing the production of propionic acid by using central composite design method. The system was found to exhibit product inhibition and hence the product inhibition kinetics was studied. A two parameter kinetic model, taking into account of the product inhibition, was proposed. Leudeking and Piret model was used to describe the production kinetics. The result from the shake-flask studies were compared with that obtained from mechanically stirred batch bioreactor and total recycle batch bioreactor.

Medium optimization for high yield production of extracellular human interferon-γ from Pichia pastoris: A statistical optimization and neural network-based approach

Medium development for high level expression of human interferon gamma (hIFN-γ) from Pichia pastoris (GS115) was performed with the aid of statistical and nonlinear modeling techniques. In the initial screening, gluconate and glycine were found to be key carbon and nitrogen sources, showing significant effect on production of hIFN-γ. Plackett-Burman screening revealed that medium components., gluconate, glycine, KH2PO4 and histidine, have a considerable impact on hIFN-γ production. Optimization was further proceeded with Box-Behnken design followed by artificial neural network linked genetic algorithm (ANN-GA). The maximum production of hIFN-γ was found to be 28.48mg/L using Box-Behnken optimization (R2=0.98), whereas the ANN-GA based optimization had displayed a better production rate of 30.99mg/L (R2=0.98), with optimal concentration of gluconate=50 g/L, glycine=10.185 g/L, KH2PO4=35.912 g/L and histidine 0.264 g/L. The validation was carried out in batch bioreactor and unstructured kinetic models were adapted. The Luedeking-Piret (L-P) model showed production of hIFN-γ was mixed growth associated with the maximum production rate of 40mg/L of hIFN-γ production.

PYRENE ENCAPSULATED ALGINATE BEAD TYPE FOR SUSTAINED RELEASE IN BIODEGRADATION: PREPARATION AND CHARACTERISTICS

A novel method for preparation of pyrene encapsulated alginate beads for controlled release delivery of pyrene is reported in this study. Five different bead types that varied on the organic phase for pyrene delivery, presence or absence of polyvinyl alcohol (PVA) and boric acid treatment were prepared. Based on the pyrene release profile, silicone oil encapsulated in PVA-alginate bead was selected where encapsulation efficiency was more than 99% without any solvent leakage. Silicone oil encapsulation was further confirmed in microscopy observations. Pyrene release behavior from the beads was explained by a diffusion controlled first order release (R2 > 0.96). Reusability of this bead was demonstrated, where pyrene was loaded from an external medium in a non-destructive way. Application of the system was finally established in a biodegradation study using Mycobacterium frederiksbergense, where simultaneous release and removal of pyrene along with appearance of pyrene metabolites was observed.

Reverse micellar extraction of papain with cationic detergent based system: An optimization approach

ABSTRACT In this study, reverse micellar extraction of papain model system was performed using cetyltrimethylammonium bromide (CTAB)/iso-octane/hexanol/butanol system to optimize the forward and back extraction efficiency (BEE). A maximum forward extraction efficiency of 55.0, 61.0, and 54% was achieved with an aqueous phase pH of 11.0, 150 mM CTAB/iso-octane and 0.1 M NaCl, respectively. Taguchi’s orthogonal array was applied to optimize the pH of stripping phase, concentration of isopropyl alcohol (IPA) and potassium chloride (KCl) for maximizing BEE. The optimal levels of stripping phase pH, concentration of IPA and KCl were found to be 6, 20% (v/v), and 0.8 M, respectively. Under these optimal levels, the BEE was found to be 88% after which enzyme activity was recovered with 2.5-fold purification. Further optimization was performed using artificial neural network-linked genetic algorithm, where the BEE was improved to 90.52% with pH 6, IPA (%) = 19.938, and KCl (M) = 0.729.