Faculty Publications

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Author: search.filters.author.Raval, K.Subject: search.filters.subject.bacterial cell

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    Expression of Bacillus licheniformis chitin deacetylase in E. coli pLysS: Sustainable production, purification and characterisation
    (Elsevier B.V., 2019) Bhat, P.; Pawaskar, G.-M.; Raval, R.; Cord-Landwehr, S.; Moerschbacher, B.; Raval, K.
    Chitosan obtained by enzymatic deacetylation of chitin using chitin deacetylase (CDA) holds promise primarily due to the possibility to yield chitosan with non-random patterns of acetylation and more environmentally friendly process compared to chemical deacetylation. In the present study, a sustainable bioprocess is reported for over-expression of a bacterial CDA in E. coli pLysS cells. A Bacillus licheniformis CDA gene is identified in the genome of the bacterium, cloned, and expressed, yielding enzymatically active recombinant protein. For enzyme production, a growth medium is formulated using carbon and nitrogen sources, which do not compete with the human food chain. The maximum enzyme activity of 320 ± 20 U/mL is achieved under optimized conditions. The CDA productivity is improved by about 23 times in shake flask culture by optimizing operating conditions and medium components. The CDA is purified and the enzyme kinetic values i.e. Km, Vmax and Kcat are reported. Also the effect of cofactors, temperature, and pH on the enzyme activity is reported. Further, economic yield is proposed for production of CDA through this bioprocess. © 2019 Elsevier B.V.
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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)