Displaying Candida antarctica lipase B on the cell surface of Aspergillus niger as a potential food-grade whole-cell catalyst

Expression of microbial lipase in filamentous fungus Aspergillus niger: a review

Lipase has high economic importance and is widely used in biodiesel, food, detergents, cosmetics, and pharmaceutical industries. The rapid development of synthetic biology and system biology has not only paved the way for comprehensively understanding the efficient operation mechanism of Aspergillus niger cell factories but also introduced a new technological system for creating and optimizing high-efficiency A. niger cell factories. In this review, all relevant data on microbial lipase enzyme sources and general properties are gathered and updated. The relationship between A. niger strain morphology and protein production is discussed. The safety of A. niger strain is investigated to ensure product safety. The biotechnologies and factors influencing lipase expression in A. niger are summarized. This review focuses on various strategies to improve lipase expression in A. niger. The summary of these methods and the application of the gene editing technology CRISPR/Cas9 system can further improve the efficiency of constructing the engineered lipase-producing A. niger.

PTCL1-EstA from Paenarthrobacter aurescens TC1, a Candidate for Industrial Application Belonging to the VIII Esterase Family

The esterase PTCL1-EstA from Paenarthrobacter aurescens TC1 was expressed in Escherichia coli and characterized. An 1152 bp open reading frame encoding a 383 amino acid polypeptide was successfully expressed, the C-terminally His6-tagged PTCL1-EstA enzyme was purified, and the predicted molecular mass of the purified PTCL1-EstA was 40.6 kDa. The EstA family serine hydrolase PTCL1-EstA belongs to the esterase family VIII, contains esterase-labeled S-C-S-K sequences, and homologous class C beta-lactamase sequences. PTCL1-EstA favored p-nitrophenyl esters with C2-C6 chain lengths, but it was also able to hydrolyze long-chain p-nitrophenyl esters. Homology modelling and substrate docking predicted that Ser59 was an active site residue in PTCL1-EstA, as well as Tyr148, Ala325, and Asp323, which are critical in catalyzing the enzymatic reaction of p-nitrophenyl esters. PTCL1-EstA reached the highest specific activity against p-nitrophenyl butyrate (C4) at pH 7.0 and 45 °C but revealed better thermal stability at 40 °C and maintained high relative enzymatic activity and stability at pH 5.0–9.0. Fermentation medium optimization for PTCL1-EstA increased the enzyme activity to 510.76 U/mL, tapping the potential of PTCL1-EstA for industrial production.

Engineering bioscaffolds for enzyme assembly

With the demand for green, safe, and continuous biocatalysis, bioscaffolds, compared with synthetic scaffolds, have become a desirable candidate for constructing enzyme assemblages because of their biocompatibility and regenerability. Biocompatibility makes bioscaffolds more suitable for safe and green production, especially in food processing, production of bioactive agents, and diagnosis. The regenerability can enable the engineered biocatalysts regenerate through simple self-proliferation without complex re-modification, which is attractive for continuous biocatalytic processes. In view of the unique biocompatibility and regenerability of bioscaffolds, they can be classified into non-living (polysaccharide, nucleic acid, and protein) and living (virus, bacteria, fungi, spore, and biofilm) bioscaffolds, which can fully satisfy these two unique properties, respectively. Enzymes assembled onto non-living bioscaffolds are based on single or complex components, while enzymes assembled onto living bioscaffolds are based on living bodies. In terms of their unique biocompatibility and regenerability, this review mainly covers the current advances in the research and application of non-living and living bioscaffolds with focus on engineering strategies for enzyme assembly. Finally, the future development of bioscaffolds for enzyme assembly is also discussed. Hopefully, this review will attract the interest of researchers in various fields and empower the development of biocatalysis, biomedicine, environmental remediation, therapy, and diagnosis.

Optimization and characterization of oligosaccharides production from citrus peel waste resource using Aspergillus niger 1805

Oligosaccharides have many growth-promoting properties for crops and are effective for fighting off various diseases in agriculture. Producing oligosaccharides from waste fruit peel by using food microorganisms will be a potential approach to provide the high-value products for sustainable development of green agriculture. Aspergillus niger 1805 was isolated from citrus peel and identified by internal transcribed spacer (ITS1-ITS4) sequencing. A. niger 1805 grew well only with waste citrus peel (WCP) as the sole medium. >50% WCP was degraded into oligosaccharides by fermentation with A. niger at 37 °C, pH 5.0 and 4 mM Ca²⁺ within 72 h, and oligosaccharide yield rate of >40%. Most oligosaccharides were in the form of Nano-size particles [10-500 nm]. Kolmogorov-Smirnov Goodness of Fit Test (KS test) showed that the distribution of the oligosaccharide micro-particles fitted a lognormal model (p > .05). Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analysis showed that the oligosaccharides were mainly comprised of glucose polymer with degrees of polymerization (DP) of 4-17. A. niger 1805 is a potential tool to produce oligosaccharides from WCP.

Cell surface display of proteins on filamentous fungi

Protein display approaches have been useful to endow the cell surface of yeasts with new catalytic activities so that they can act as enhanced whole-cell biocatalysts. Despite their biotechnological potential, protein display technologies remain poorly developed for filamentous fungi. The lignocellulolytic character of some of them coupled to the cell surface biosynthesis of valuable molecules by a single or a cascade of several displayed enzymes is an appealing prospect. Cell surface protein display consists in the co-translational fusion of a functional protein (passenger) to an anchor one, usually a cell-wall-resident protein. The abundance, spacing, and local environment of the displayed enzymes-determined by the relationship of the anchor protein with the structure and dynamics of the engineered cell wall-are factors that influence the performance of display-based biocatalysts. The development of protein display strategies in filamentous fungi could be based on the field advances in yeasts; however, the unique composition, structure, and biology of filamentous fungi cell walls require the customization of the approach to those microorganisms. In this prospective review, the cellular bases, the design principles, and the available tools to foster the development of cell surface protein display technologies in filamentous fungi are discussed.

Expression and display of a novel thermostable esterase from Clostridium thermocellum on the surface of Bacillus subtilis using the CotB anchor protein

Esterases expressed in microbial hosts are commercially valuable, but their applications are limited due to high costs of production and harsh industrial processes involved. In this study, the esterase-DSM (from Clostridium thermocellum) was expressed and successfully displayed on the spore surface, and the spore-associated esterase was confirmed by western blot analysis and activity measurements. The optimal temperature and pH of spore surface-displayed DSM was 60 and 8.5 °C, respectively. It also demonstrates a broad temperature and pH optimum in the range of 50–70, 7–9.5 °C. The spore surface-displayed esterase-DSM retained 78, 68 % of its original activity after 5 h incubation at 60 and 70 °C, respectively, which was twofold greater activity than that of the purified DSM. The recombinant spores has high activity and stability in DMSO, which was 49 % higher than the retained activity of the purified DSM in DMSO (20 % v/v), and retained 65.2 % of activity after 7 h of incubation in DMSO (20 % v/v). However, the recombinant spores could retain 77 % activity after 3 rounds of recycling. These results suggest that enzyme displayed on the surface of the Bacillus subtilis spore could serve as an effective approach for enzyme immobilization.

Performance in synthetic applications of a yeast surface display-based biocatalyst

Organic synthesis with surface-displayed lipase: alkyl esters of fatty acids. Compared performance to commercial preparations. Catalyst is reusable and stable up to 50–60 °C. Kinetics of surface-displayed synthesis of butyl decanoate.

Characterization, performance, and applications of a yeast surface display-based biocatalyst

Yeast surface display (YSD) of two lipases. Measured expression level and copy number. Synthetic and hydrolytic activity comparable to commercial lipase. Cost analysis of YSD system vs. commercial formulations.