Discovery and characterization of a novel protease from the Antarctic soil

Extracellular proteases from halophiles: diversity and application challenges

Halophilic extracellular proteases offer promising application in various fields. Information on these prominent proteins including the synthesizing organisms, biochemical properties, domain organisation, purification, and application challenges has never been covered in recent reviews. Although extracellular proteases from bacteria pioneered the study of proteases in halophiles, progress is being made in proteases from halophilic archaea. Recent advances in extracellular proteases from archaea revealed that archaeal proteases are more robust and applicable. Extracellular proteases are composed of domains that determine their mechanisms of action. The intriguing domain structure of halophilic extracellular proteases consists of N-terminal domain, catalytic domain, and C-terminal extension. The role of C-terminal domains varies among different organisms. A high diversity of C-terminal domains would endow the proteases with diverse functions. With the development of genomics, culture-independent methods involving heterologous expression, affinity chromatography, and in vitro refolding are deployed with few challenges on purification and presenting novel research opportunities. Halophilic extracellular proteases have demonstrated remarkable potentials in industries such as detergent, leather, peptide synthesis, and biodegradation, with desirable properties and ability to withstand harsh industrial processes. KEY POINTS: • Halophilic extracellular proteases have robust properties suitable for applications. • A high diversity of C-terminal domains may endow proteases with diverse properties. • Novel protease extraction methods present novel application opportunities.

Characterization of effector protein Hap determining meat spoilage process from meat-borne Aeromonas salmonicida

The spoilage roles of effector proteins secreted by dominant spoilage bacteria during food spoilage remained unknown. In this investigation, a hemagglutinin protease (Hap) belonging to the M4 family metallopeptidase was identified from Aeromonas salmonicida 29 isolate. It, has a molecular weight of 33.5 kDa, a V_max of 17.06 μg/mL/min, and a K_m of 2.46 mg/mL, and is conserved in various dominant spoilage bacteria. The stability testing demonstrated that Hap could maintain specific activity in the common environments (pH, temperature, and metal ions) of chilled meat. It exhibited high spoilage ability on meat in situ, increasing TVB-N, pH values, and the production of volatile organic compounds (VOCs), which was consistent with proteolytic activity analysis, completely confirming the determinant role of Hap for meat spoilage. These observations will enrich the spoilage theory and provide new insights into the control of food quality and safety.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

Metagenomic Approaches as a Tool to Unravel Promising Biocatalysts from Natural Resources: Soil and Water

Natural resources are considered a promising source of microorganisms responsible for producing biocatalysts with great relevance in several industrial areas. However, a significant fraction of the environmental microorganisms remains unknown or unexploited due to the limitations associated with their cultivation in the laboratory through classical techniques. Metagenomics has emerged as an innovative and strategic approach to explore these unculturable microorganisms through the analysis of DNA extracted from environmental samples. In this review, a detailed discussion is presented on the application of metagenomics to unravel the biotechnological potential of natural resources for the discovery of promising biocatalysts. An extensive bibliographic survey was carried out between 2010 and 2021, covering diverse metagenomic studies using soil and/or water samples from different types and locations. The review comprises, for the first time, an overview of the worldwide metagenomic studies performed in soil and water and provides a complete and global vision of the enzyme diversity associated with each specific environment.