Heterologous Expression and Structural Elucidation of a Highly Thermostable Alkaline Serine Protease from Haloalkaliphilic Actinobacterium, Nocardiopsis sp. Mit-7

In-vitro and in-silico antibacterial and antibiofilm activities of an aromatic heterocyclic metabolite from a novel halo-thermophilic Streptomyces sp. strain CBN-1 against bacteria causing nosocomial infections

BACKGROUND

Multidrug-resistant and biofilm-forming pathogens have become a global health challenge, contributing to persistent and hard-to-treat infections. The objective of this study was to characterize an active metabolite produced by a novel halo-thermophilic Streptomyces sp. CBN-1 that exhibits potent antibacterial and antibiofilm activities using a combined in-silico and experimental approach.

METHODS & RESULTS

In this study, a halo-thermophilic Streptomyces sp. CBN-1 strain was selected for its ability to grow in 10% NaCl at 40 °C. This strain was identified using phenotypic characterizations and 16S rRNA gene sequence analysis as Streptomyces rochei NRRL B-2410 with 99.15% similarity. An active metabolite, CBNa-1, was extracted using n-butanol solvent from ISP2 broth medium and purified by HPLC. Structural characterization using electrospray ionization mass spectrometry and NMR spectroscopy identified CBNa-1 as an aromatic heterocyclic compound regulated by non-ribosomal peptide synthetase (NRPS) and type II polyketide synthase (PKS) genes. It exhibited potent activity with minimum inhibitory concentrations (MIC) ranging from 4 to 5 µg/mL and minimum biofilm inhibitory concentrations (MBIC50%) at ½ MIC. Additionally, in-silico docking analyses showed that CBNa-1 had stronger binding affinities from - 8.7 to -8.1 kcal/mol with isoleucyl-tRNA synthetase, glucosamine-6-phosphate synthase, penicillin-binding protein 1a, type II DNA topoisomerases, and quorum sensing compared to antibiotics (-5.7 to -7.9 kcal/mol). Furthermore, molecular dynamic (MD) simulation showed the stability of the protein-ligand complex under physiological conditions.

CONCLUSION

This study reports the first identification of CBNa-1, a metabolite from prokaryotic cells, with potent antibacterial and anti-biofilm properties to combat nosocomial infections caused by MDR pathogens, including bacteria resistant to third-generation cephalosporins.

Advances in Microbial Alkaline Proteases: Addressing Industrial Bottlenecks Through Genetic and Enzyme Engineering

Microbial alkaline proteases are versatile enzymes chiefly employed in various industrial sectors, viz., food processing, detergents, leather, textile, pharmaceutical industries. However, the existing bottlenecks, such as lower enzyme yields, stability, purification, specificity, and catalytic rates, bring resistance toward their industrial suitability. The robust microbes are prominent sources of stable enzymes. However, further challenges may exist, such as low yield, difficult purification, and lesser enzymatic efficiency. With the advent of advanced genomic and enzyme engineering approaches, such bottlenecks can be overcome. Initially, the microbial genomes can be used as novel repositories for stable enzyme sequences for further heterologous production with higher enzymatic yields and an easier purification process. Moreover, enzyme improvement through directed evolution and rational engineering could enhance enzyme stability and efficiency. Currently, conventional enzyme improvement methods are increasingly replaced by Artificial Intelligence-Machine Learning (AI-ML) and computational data-driven tools that provide precise information for tailoring enzymes for industrial endeavors. Hence, the current review encompasses a deliberate study of microbial alkaline proteases, their major industrial applications, and the bottlenecks in their commercial implementations. Further, it presents in-detailed solutions, including genetic and enzyme engineering, and insights toward incorporating advanced tools like AI-ML and de novo enzyme engineering to subside the existing challenges.