Screening, identification, and characterization of lipase-producing halotolerant Bacillus altitudinis Ant19 from Antarctic soil

Discovery and Mechanistic Understanding of a Lipase from Rhizorhabdus dicambivorans for Efficient Ester Aminolysis in Aromatic Amines

The formation of amide bonds via aminolysis of esters by lipases generates a diverse range of amide frameworks in biosynthetic chemistry. Few lipases have satisfactory activity towards bulky aromatic amines despite numerous attempts to improve the efficiency of this transformation. Here, we report the discovery of a new intracellular lipase (Ndbn) with a broad substrate scope. Ndbn turns over a range of esters and aromatic amines in the presence of water (2 %; v/v), producing a high yield of multiple valuable amides. Remarkably, a higher conversion rate was observed for the synthesis of amides from substrates with aromatic amine rather than aliphatic amines. Molecular dynamics (MD) and quantum mechanical/molecular mechanical (QM/MM) studies showcase the mechanism for the preference for aromatic amines, including a more suitable orientation, shorter catalytic distances in the active site pocket and a lower reaction barrier for aromatic than for aliphatic amines. This unique lipase is thus a promising biocatalyst for the efficient synthesis of aromatic amides.

Overexpression and truncation of a novel cold-adapted lipase with improved enzymatic characteristics

The novel cold-adapted lipase (Lip ZC12) derived from Psychrobacter sp. ZY124 exhibited higher catalytic activity at 20-40 °C, the whole gene was then sequenced, analyzed, and overexpressed. However, its intrinsic structural characteristics lead to a decreased affinity toward the substrate, thus limiting the improvement of catalytic efficiency. Modeling the homologous structure and simulating the binding process of Lip ZC12 with the substrate. It was found that truncated lid (lip-Δlid) could not only increase the kcat, but also significantly enhance the substrate affinity, the substrate affinity and catalytic efficiency of Lip ZC12 modified by lid truncation were significantly improved. The results revealed that the kcat/Km value of lip-Δlid was 1.6 times higher than that of free lipase. This improved catalytic performance of cold-adapted lipase, and these findings laid an important foundation for further application.

Preparation and Characterization of Carrageenase Immobilized onto Polyethyleneimine-Modified Pomelo Peel

In this study, carrageenase immobilization was evaluated with a concise and efficient strategy. Pomelo peel cellulose (PPC) modified by polyethyleneimine (PEI) using the physical absorption method was used as a carrier to immobilize carrageenase and achieved repeated batch catalysis. In addition, various immobilization and reaction parameters were scrutinized to enhance the immobilization efficiency. Under the optimized conditions, the enzyme activity recovery rate was more than 50% and 4.1 times higher than immobilization with non-modified pomelo peels. The optimum temperature and pH of carrageenase after immobilization by PEI-modified pomelo peel, at 60°C and 7.5 respectively, were in line with the free enzyme. The temperature resistance was reduced, inconsistent with free enzyme, and pH resistance was increased. A significant loss of activity (46.8%) was observed after reusing it thrice under optimal reaction conditions. In terms of stability, the immobilized enzyme conserved 76.0% of the initial enzyme activity after 98 days of storage. Furthermore, a modest decrease in the kinetic constant (Km) value was observed, indicating the improved substrate affinity of the immobilized enzyme. Therefore, modified pomelo peel is a verified and promising enzyme immobilization system for the synthesis of inorganic solvents.

Comprehensive insights on environmental adaptation strategies in Antarctic bacteria and biotechnological applications of cold adapted molecules

Climate change and the induced environmental disturbances is one of the major threats that have a strong impact on bacterial communities in the Antarctic environment. To cope with the persistent extreme environment and inhospitable conditions, psychrophilic bacteria are thriving and displaying striking adaptive characteristics towards severe external factors including freezing temperature, sea ice, high radiation and salinity which indicates their potential in regulating climate change's environmental impacts. The review illustrates the different adaptation strategies of Antarctic microbes to changing climate factors at the structural, physiological and molecular level. Moreover, we discuss the recent developments in "omics" approaches to reveal polar "blackbox" of psychrophiles in order to gain a comprehensive picture of bacterial communities. The psychrophilic bacteria synthesize distinctive cold-adapted enzymes and molecules that have many more industrial applications than mesophilic ones in biotechnological industries. Hence, the review also emphasizes on the biotechnological potential of psychrophilic enzymes in different sectors and suggests the machine learning approach to study cold-adapted bacteria and engineering the industrially important enzymes for sustainable bioeconomy.