Utilization of Shrimp waste as a novel media for marine bacteria isolation

Eco-friendly and safe alternatives for the valorization of shrimp farming waste

The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Cloning, expression, purification and characterization of chitin deacetylase extremozyme from halophilic Bacillus aryabhattai B8W22

Chitin deacetylase (CDA) (EC 3.5.1.41) is a hydrolytic enzyme that belongs to carbohydrate esterase family 4 as per the CAZY database. The CDA enzyme deacetylates chitin into chitosan. As the marine ecosystem is a rich source of chitin, it would also hold the unexplored extremophiles. In this study, an organism was isolated from 40 m sea sediment under halophilic condition and identified as Bacillus aryabhattai B8W22 by 16S rRNA sequencing. The CDA gene from the isolate was cloned and overexpressed in E. coli Rosetta pLysS and purified using a Ni-NTA affinity chromatography. The enzyme was found active on both ethylene glycol chitin (EGC) and chitooligosaccharides (COS). The enzyme characterization study revealed, maximum enzyme velocity at one hour, optimum pH at 7 with 50 mM Tris-HCl buffer, optimum reaction temperature of 30 ºC in standard assay conditions. The co-factor screening affirmed enhancement in the enzyme activity by 142.43 ± 7.13% and 146.88 ± 4.09% with substrate EGC and COS, respectively, in the presence of 2 mM Mg2+. This activity was decreased with the inclusion of EDTA and acetate in the assay solutions. The enzyme was found to be halotolerant; the relative activity increased to 116.98 ± 3.87% and 118.70 ± 0.98% with EGC and COS as substrates in the presence of 1 M NaCl. The enzyme also demonstrated thermo-stability, retaining 87.27 ± 2.85% and 94.08 ± 0.92% activity with substrate EGC and COS, respectively, upon treatment at 50 ºC for 24 h. The kinetic parameters K m, V max, and K cat were 3.06E-05 µg mL-1, 3.06E + 01 µM mg-1 min-1 and 3.27E + 04 s-1, respectively, with EGC as the substrate and 7.14E-07 µg mL-1, 7.14E + 01 µM mg-1 min-1 and 1.40E + 06 s-1, respectively, with COS as the substrate. The enzyme was found to be following Michaelis-Menten kinetics with both the polymeric and oligomeric substrates. In recent years, enzymatic conversion of chitosan is gaining importance due to its known pattern of deacetylation and reproducibility. Thus, this BaCDA extremozyme could be used for industrial production of chitosan polymer as well as chitosan oligosaccharides for biomedical application.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03073-3.

Bio-prospecting the future in perspective of amidohydrolase L-glutaminase from marine habitats

In the current scenario, considerable attention is being given to the enzyme L-glutaminase (EC 3.5.1.2). It belongs to the amidohydrolase class adherent to the family of serine-reliant β-lactamases and the penicillin-binding proteins due to its higher affinity to polymerize and modify peptidoglycan synthesis. However, based on the catalytic proficiency, L-glutaminase is characterized as a proteolytic endopeptidase that cleaves peptide linkage and emancipates various byproducts, viz. ammonia along with glutamate. L-glutamine is considered the key amino acid reportedly involved in multiple metabolic pathways such as nitrogen metabolism. The present review is focused on the recent development and aspects concomitant to the biotechnological applicability of L-glutaminase predominantly from the marine habitat. Additionally, a majority of L-glutaminases finds application in cancer therapy as therapeutic agents, especially for acute lymphocytic leukaemia. The in vitro studies have been effective against various human cancer cell lines. L-glutaminase enhances the growth of probiotic bacteria. Apart from all these applications, it is suitably applicable in fermented foods as a flavour enhancer especially the umami flavour and content. Marine habitats have largely been exploited for their bio-catalytic potential but very scarcely for therapeutic enzymes. Some of the reports of such marine bacterial isolates from Bacillus sp., Pseudomonas sp. and Vibrio sp. are in the domain, but none highlights the therapeutic applications predominantly as anticancer and anti-proliferative agents. KEY POINTS: The exploration of marine habitats along the Gujarat coasts mainly for bacteria secreting L-glutaminase is scarcely reported, and even more scarce are the amidohydrolases from these marine niches as compared to their terrestrial counterparts. Microbial sourced amidohydrolase has wide bio-applicability that includes food, cosmetics and therapeutics especially as anticancer/anti-proliferative agent making it of immense biotechnological significance.