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    Screening and optimisation of bioconversion parameters for the reduction of 3-[5-[(4-flurophenyl)-1,5, di-oxopentol]-yl] -4-(S) phenyl oxazolidin-2-one
    (2009) Brahmani Priyadarshini, S.R.; Mugeraya, G.; Sandhyavali, M.S.
    The reduction of ketones is one of the most important and practical reaction for producing non racemic alcohols, which are needed to synthesize industrially important chemicals such as pharmaceuticals, agrochemicals and natural products. Biocatalysis has turned out to be a highly competitive technology for asymmetric ketone reduction. In the present work, an attempt was made to identify a potential microorganism for the reduction of 3-[5-[(4-flurophenyl)-1,5, di-oxopentol]-yl] -4-(S) phenyl oxazolidin-2-one. Some of the fungi screened were Saccharomyces cerevisiae, Aspergillus niger(2 strains), Pichia farinosa, Candida vishwanathii, Rhizopus stolonifer and Penicillin species. The experimental results showed that S. cerevisiae, Aspergillus niger and C. viswanathii strains were able to bring about the conversion of selected ketone to alcohol. As Saccharomyces cerevisiae was found to be more effective in bringing about reduction, it was selected for further experiment. In order to improve the yield certain bioconversion parameters like pH of reaction medium, time of incubation, incubation temperature and biomass to substrate ratio were studied. The results showed that the bioreduction of the above mentioned substrate was maximum in pH 7.6 at 30°C when incubated for 48 h. The conversion increased with increase in biomass, however it reached saturation at the ratio of 300:1.
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    Lipase mediated synthesis of rutin fatty ester: Study of its process parameters and solvent polarity
    (Elsevier Ltd, 2017) Chandrasekar, C.; Belur, P.D.; Iyyaswami, R.
    Lipophilization of antioxidants is recognized as an effective strategy to enhance solubility and thus effectiveness in lipid based food. In this study, an effort was made to optimize rutin fatty ester synthesis in two different solvent systems to understand the influence of reaction system hydrophobicity on the optimum conditions using immobilised Candida antartica lipase. Under unoptimized conditions, 52.14% and 13.02% conversion was achieved in acetone and tert-butanol solvent systems, respectively. Among all the process parameters, water activity of the system was found to show highest influence on the conversion in each reaction system. In the presence of molecular sieves, the ester production increased to 62.9% in tert-butanol system, unlike acetone system. Under optimal conditions, conversion increased to 60.74% and 65.73% in acetone and tert-butanol system, respectively. This study shows, maintaining optimal water activity is crucial in reaction systems having polar solvents compared to more non-polar solvents. © 2017 Elsevier Ltd
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    Enhancement of n-3 polyunsaturated fatty acid glycerides in Sardine oil by a bioimprinted cross-linked Candida rugosa lipase
    (Elsevier Inc. usjcs@elsevier.com, 2018) Sampath, C.; Belur, P.D.; Iyyaswami, R.
    Considering the advantages of bioimprinting and carrier free immobilization, cross-linked enzyme aggregates (CLEA) were prepared by using bioimprinted Candida rugosa lipase (CRL) with Bovine serum albumin (BSA), Polyethyleneimine and glutaraldehyde. Effect of various factors such as CRL-Oleic acid ratio, CRL-BSA ratio, CRL- Polyethyleneimine ratio, glutaraldehyde loading, cross-linking time etc., on lipase activity recovery and aggregate yield were studied and optimized. This immobilized lipase (CRL-CLEA) was used for the selective hydrolysis of ester linkages of non-PUFA glycerides, with an aim to concentrate EPA and DHA glycerides in the Sardine oil. Imprinting with oleic acid in the presence of ethanol and Tween 60, and further immobilization with co-aggregates and cross-linking agent showed 10.4 times higher degree of hydrolysis compared to free enzyme. As result, 2.83-fold increase of n-3 PUFA content in deacidified oil was obtained by using CRL-CLEA. The resultant oil had negligible di- and triglycerides content, proving higher efficiency in hydrolysing ester bonds of fatty acids, other than n-3 PUFA. Reusability studies showed CRL-CLEA could be reused up to 5 runs without a substantial reduction in its performance. Improvement in degree of hydrolysis, thermostability, efficiency of hydrolysis and reusability were achieved due to bioimprinting and subsequent immobilization of CRL in the form of CLEA. © 2017 Elsevier Inc.
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    Identification and characterization of chitinase producing marine microorganism: Unleashing the potential of chitooligosaccharides for bioethanol synthesis
    (Elsevier B.V., 2024) Atheena, P.V.; Rajesh, K.M.; Raval, K.; Subbalaxmi, S.; Raval, R.
    The dwindling supply of the petroleum product and its carbon footprint has initiated search for a sustainable fuel and alternate feed-stocks. One such underexplored feedstock is chitin, a waste derived from sea food processing. The limitation of insolubility and crystallinity inherent in chitin is addressed with the chitin hydrolysates. In the present study, a chitinases producing marine isolate was isolated from the sediments of Arabian Sea from a depth of 20 m. In order to increase the expression of the chitinases, sequential optimisation using one factor at a time and Taguchi experimental designs were employed which resulted in a yield of 13.46 U/mL which was 2.62 fold higher than the initial bioprocess condition values. In a two-step refinery protocol, Candida albicans was evolved towards chitooligosaccharides using chemically synthesized hydrolysates. In a fed –batch fermentation design the Candida yielded a 12.8 % conversion of these commercial chitin oligosaccharides into bioethanol in a run time of 48 h. This is the first report demonstrating the potential of Candida to utilise chitin oligosaccharides for the production of bioethanol. © 2024 The Author(s)
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    Identification, purification and functional characterization of a thermostable marine chitinase for potential fungal control via chitin degradation mechanism
    (Elsevier Ltd, 2025) Atheena, P.V.; Raval, K.; Raval, R.
    The growing prevalence of treatment-resistant Candida species highlights an urgent need for innovative antifungal therapies. The current range of antifungals, limited to polyenes, azoles, and echinocandins, are becoming insufficient due to the rise of resistance, including cross-resistance among fungal strains. Marine environment is an underexplored reservoir of unique enzymes which can be extremophilic. This study presents the cloning and expression of a chitinase gene from the bacterium Bacillus thuringiensis (BtChi), expressed in an E. coli system, yielding a protein with a molecular weight of approximately 71 kDa. Disc diffusion and MIC experiments indicated that 5 ?g/mL chitinase efficiently suppressed the growth of Candida albicans. Initial characterization identified the optimal activity at 40 °C and pH 7.0. The enzyme retained over 75 % activity across a pH range of 4–8 and a temperature range of 30–70 °C after 120 min. Activity was further enhanced by 24 % with 100 mM Na+. Kinetic parameters with colloidal chitin revealed Km and Vmax values to be 0.05 mg/mL and 1.37 U/mL respectively. This study holds the potential of developing a potent natural anti-fungal against the present day chemical counterparts. © 2025 The Authors