Improved Thermal Stability of a Novel Acidophilic Phytase

Phytase increases the availability of phosphate and trace elements by hydrolyzing the phosphomonoester bond in phytate present in animal feed. It is also an important enzyme from an environmental perspective because it not only promotes the growth of livestocks but also prevents phosphorus contamination released into the environment. Here we present a novel phytase derived from Turicimonas muris, TmPhy, which has distinctive structure and properties compared to other previously known phytases. TmPhy gene expressed in the Pichia system was confirmed to be 41 kDa in size and was used in purified form to evaluate optimal conditions for maximum activity. TmPhy has a dual optimum pH at pH3 and pH6.8 and exhibited the highest activity at 70°C. However, the heat tolerance of the wildtype was not satisfactory for feed application. Therefore, random mutation, disulfide bond introduction, and N-terminal mutation were performed to improve the thermostability of the TmPhy. Random mutation resulted in TmPhyM with about 45% improvement in stability at 60°C. Through further improvements, a total of three mutants were screened and their heat tolerance was evaluated. As a result, we obtained TmPhyMD1 with 46.5% residual activity, TmPhyMD2 with 74.1%, and TmPhyMD3 with 66.8% at 80°C heat treatment without significant loss of or with increased activity.

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.

Biochemical characterization of a key laccase-like multicopper oxidase of artificially cultivable Morchella importuna provides insights into plant-litter decomposition

The aim of this study is to determine the key laccase-encoding gene in the life cycle of Morchella importuna SCYDJ1-A1, and to characterize the biochemical properties of the laccase. Two laccase-like multicopper oxidase (LMCO) genes were identified in the genome of M. importuna SCYDJ1-A1 as putative laccase-encoding genes. The two genes, belonging to Auxiliary Activity family 1 subfamily 3, were named as MiLacA and MiLacB. Phylogenetic analysis of deduced amino acid sequences showed that MiLacA is closest to a LMCO of M. importuna 22J1, while MiLacB had low similarity with known Morchella LMCOs. Real-time quantitative PCR results showed that MiLacA was expressed at much higher levels than MiLacB throughout the entire course of artificial cultivation. MiLacA was overexpressed in Pichia pastoris as a recombinant protein. Biochemical characterization of the purified enzyme showed that MiLacA simultaneously possessed laccase and polyphenol-oxidase activities. MiLacA could be strongly inhibited by Fe²⁺, which is unusual. The optimum pH was four and optimum temperature was 60 °C. The enzyme retained over 74% of the laccase activity after 16-h incubation at 60 °C, which means that its thermostability is at the forefront among the currently known laccases. Our findings may help to elucidate how the laccase of M. importuna is involved in decaying lignin in plant litter, and could also provide a candidate thermostable laccase for potential industrial application.

Microbial phytase: Impact of advances in genetic engineering in revolutionizing its properties and applications

Phytases are enzymes that increase the availability of phosphorous in monogastric diet and reduces the anti-nutrition effect of phytate. This review highlights contributions of recombinant technology to phytase research during the last decade with specific emphasis on new generation phytases. Application of modern molecular tools and genetic engineering have aided the discovery of novel phytase genes, facilitated its commercial production and expanded its applications. In future, by adopting most recent gene improvement techniques, more efficient next generation phytases can be developed for specific applications.

Engineering of Yersinia Phytases to Improve Pepsin and Trypsin Resistance and Thermostability and Application Potential in the Food and Feed Industry

Susceptibility to proteases usually limits the application of phytase. We sought to improve the pepsin and trypsin resistance of YeAPPA from Yersinia enterocolitica and YkAPPA from Y. kristensenii by optimizing amino acid polarity and charge. The predicted pepsin/trypsin cleavage sites F89/K226 in pepsin/trypsin-sensitive YeAPPA and the corresponding sites (F89/E226) in pepsin-sensitive but trypsin-resistant YkAPPA were substituted with S and H, respectively. Six variants were produced in Pichia pastoris for catalytic and biochemical characterization. F89S, E226H, and F89S/E226H elevated pepsin resistance and thermostability and K226H and F89S/K226H improved pepsin and trypsin resistance and stability at 60 °C and low pH. All the variants increased the ability of the proteins to hydrolyze phytate in corn meal by 2.6-14.9-fold in the presence of pepsin at 37 °C and low pH. This study developed a genetic manipulation strategy specific for pepsin/trypsin-sensitive phytases that can improve enzyme tolerance against proteases and heat and benefit the food and feed industry in a cost-effective way.