Degradation of marine crustacean shell wastes through single-stage co-fermentation using proteolytic and chitinolytic bacteria.

Management of crustacean shell waste (SW) through an eco-friendly technique is an environmental obligation to control pollution. The present study showed a novel approach through the simultaneous application of proteolytic and chitinolytic bacteria to effectively degrade unprocessed crustacean SW. For this, the bacteria with concurrent chitinolytic and proteolytic activity (Bacillus subtilis, Priestia megaterium, or Bacillus amyloliquefaciens) were applied either alone or in combination with one proteolytic strain (Paenibacillus alvei) in the unprocessed lobster, crab, and shrimp SW. The method degraded the shells with high deproteinization (> 90%) and demineralization efficiency (> 90%). The degradation was confirmed through scanning electron microscopy. The highest weight loss achieved with shrimp, crab, and lobster shells was 93.67%, 82.60%, and 83.33%, respectively. B. amyloliquefaciens + P. alvei combination produced the highest weight loss in crab and lobster SW, whereas all combinations produced statistically similar weight loss in shrimp SW. There was a concurrent production of N-acetyl glucosamine (up to 532.89, 627.87, and 498.95 mg/g of shrimp, lobster, and crab shell, respectively, with P. megaterium + P. alvei and B. amyloliquefaciens + P. alvei in all SW) and amino acids (4553.8, 648.89, 957.27 µg/g of shrimp, lobster, and crab shells, respectively with B. subtilis + P. alvei in shrimp and B. amyloliquefaciens + P. alvei in crab and lobster). Therefore, it is concluded that, for the first time, efficient degradation of crustacean shell waste was observed using chitinolytic and proteolytic bacterial fermentation with the obtention of byproducts, providing a basis for further application in SW management.

Analysis of nonribosomal peptide synthetase genes in haemolymph microbes of marine crabs.

Nonribosomal peptide synthetases (NRPS) are multi-domain enzymes that have innumerably beneficial health applications. Realizing the significance of marine microorganisms in search for NRPS sequences, study was conducted for analysis of NRPS gene sequences of marine crab haemolymph bacteria for the first time. Strains belonging to five different species were found to have NRPS genes. The study generated NRPS sequences from four bacterial species, for which NRPS gene information was not available earlier. Two new putative adenylation domain signatures were identified from phylum Firmicutes. In silico analysis of amino acid sequences from four species showed less identity (42-50%) to the characterized NRPS compounds that integrate serine residue in active site, suggesting the novelty or uncharacterized nature. Altogether, the study warrants future research exploiting marine crab haemolymph bacteria, an unexplored niche of microbial genetic wealth to discover microbial novel NRPS genes and natural products using emerging tools and technologies.