Antioxidant and Anticancer Properties of Biosynthesized GA/Ag-Fe3O4@ Nanocomposites

Enhancement of mono-acylated MEL-D production in an acyltransferase gene-deleted strain of Pseudozyma tsukubaensis by supplementation with di-acylated MEL-B in culture medium

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by various yeasts. MEL producers produce mainly di-acylated MELs (consisting of two fatty acid chains). Among them, Pseudozyma tsukubaensis is a di-acylated MEL-B (d-MEL-B) producer. In a previous study, we generated an acyltransferase-deleted strain of P. tsukubaensis (ΔPtMAC2), which selectively produced mono-acylated MEL-D (m-MEL-D, consisting of one fatty acid chain), but not d-MEL-B. However, m-MEL-D productivity in ΔPtMAC2 was low, and oil consumption was significantly reduced compared to the parent strain. Based on these findings, we hypothesized that the d-MEL-B produced by the parent strain may act as an emulsifier in the culture medium, leading to easier utilization of the oil. By contrast, the m-MEL-D produced by ΔPtMAC2 may not have the ability to emulsify oil, thus the oil is used inefficiently and productivity of m-MEL-D is low. Therefore, we expected that adding d-MEL-B to the culture medium during ΔPtMAC2 cultivation would increase m-MEL-D production. To enhance the oil consumption and m-MEL-D production of ΔPtMAC2, d-MEL-B and chemical surfactants were added to the culture medium as emulsifiers during ΔPtMAC2 cultivation. Adding d-MEL-B enhanced both the oil consumption and m-MEL-D production of ΔPtMAC2; Tween 20 and Triton X-100 also showed enhancement effects. As expected, d-MEL-B, Tween20 and TritonX-100, showed marked olive oil emulsification activity, whereas m-MEL-D did not. These results strongly support our hypothesis and significantly improve m-MEL-D productivity.

Characterization of a KU70-disrupted strain of the mannosylerythritol lipid-producing yeast Pseudozyma tsukubaensis constructed by a marker recycling system

The basidiomycetous yeast Pseudozyma tsukubaensis is known as an industrial mannosylerythritol lipid producer. In this study, the PtURA5 marker gene was deleted by homologous recombination. Using the PtURA5-deleted mutant as a host strain, we obtained a derivative disrupted for the PtKU70 gene, a putative ortholog of the KU70 gene encoding a protein involved in the nonhomologous end-joining pathway of DNA repair. Subsequently, the introduced PtURA5 gene was re-deleted by marker recycling. These results demonstrated that the PtURA5 gene can be used as a recyclable marker gene. Although the frequency of homologous recombination has been shown to be increased by KU70 disruption in other fungi, the PtKU70-disrupted strain of P. tsukubaensis did not demonstrate an elevated frequency of homologous recombination. Furthermore, the PtKU70-disrupted strain did not show increased susceptibility to bleomycin. These results suggested that the function of this KU70 ortholog in P. tsukubaensis is distinct from that in other fungi.

Eco-friendly bio-nanocomposites: pioneering sustainable biomedical advancements in engineering

Biomedical nanocomposites, which are an upcoming breed of mischievous materials, have ushered in a new dimension in the healthcare sector. Incorporating these materials tends to boost features this component already possesses and give might to things these components could not withstand alone. The biopolymer, which carries the nanoparticles, can simultaneously improve the composite's stiffness and biological characteristics, and vice versa. This increases the options of the composite and the number of times it can be used. The bio-nanocomposites and nanoparticles enable the ecocompatibility of the medicine in their biodegradability, and they, in this way, have ecological sustainability. The outcome is the improved properties of medicine and its associated positive impact on the environment. They have broad applications in antimicrobial agents, drug carriers, tissue regeneration, wound care, dentistry, bioimaging, and bone filler, among others. The dissertation on the elements of bio-nanocomposites emphasizes production techniques, their diverse applications in medicine, match-up issues, and future-boasting prospects in the bio-nanocomposites field. Through the utilization of such materials, scientists can develop more suitable for the environment and healthy biomedical solutions, and world healthcare in this way improves as well.

Promising Application, Efficient Production, and Genetic Basis of Mannosylerythritol Lipids

Mannosylerythritol lipids (MELs) are a class of glycolipids that have been receiving increasing attention in recent years due to their diverse biological activities. MELs are produced by certain fungi and display a range of bioactivities, making them attractive candidates for various applications in medicine, agriculture, and biotechnology. Despite their remarkable qualities, industrial-scale production of MELs remains a challenge for fungal strains. Excellent fungal strains and fermentation processes are essential for the efficient production of MELs, so efforts have been made to improve the fermentation yield by screening high-yielding strains, optimizing fermentation conditions, and improving product purification processes. The availability of the genome sequence is pivotal for elucidating the genetic basis of fungal MEL biosynthesis. This review aims to shed light on the applications of MELs and provide insights into the genetic basis for efficient MEL production. Additionally, this review offers new perspectives on optimizing MEL production, contributing to the advancement of sustainable biosurfactant technologies.

Structural identification of catalytic His158 of PtMAC2p from Pseudozyma tsukubaensis, an acyltransferase involved in mannosylerythritol lipids formation

Mannosylerythritol lipids (MELs) are extracellular glycolipids produced by the basidiomycetous yeast strains. MELs consist of the disaccharide mannosylerythritol, which is acylated with fatty acids and acetylated at the mannose moiety. In the MEL biosynthesis pathway, an acyltransferase from Pseudozyma tsukubaensis, PtMAC2p, a known excellent MEL producer, has been identified to catalyze the acyl-transfer of fatty acid to the C3'-hydroxyl group of mono-acylated MEL; however, its structure remains unclear. Here, we performed X-ray crystallography of recombinant PtMAC2p produced in Escherichia coli and homogeneously purified it with catalytic activity in vitro. The crystal structure of PtMAC2p was determined by single-wavelength anomalous dispersion using iodide ions. The crystal structure shows that PtMAC2p possesses a large putative catalytic tunnel at the center of the molecule. The structural comparison demonstrated that PtMAC2p is homologous to BAHD acyltransferases, although its amino acid-sequence identity was low (<15%). Interestingly, the HXXXD motif, which is a conserved catalytic motif in the BAHD acyltransferase superfamily, is partially conserved as His158-Thr159-Leu160-Asn161-Gly162 in PtMAC2p, i.e., D in the HXXXD motif is replaced by G in PtMAC2p. Site-directed mutagenesis of His158 to Ala resulted in more than 1,000-fold decrease in the catalytic activity of PtMAC2p. These findings suggested that His158 in PtMAC2p is the catalytic residue. Moreover, in the putative catalytic tunnel, hydrophobic amino acid residues are concentrated near His158, suggesting that this region is a binding site for the fatty acid side chain of MEL (acyl acceptor) and/or acyl-coenzyme A (acyl donor). To our knowledge, this is the first study to provide structural insight into the catalytic activity of an enzyme involved in MEL biosynthesis.

Improvement of Oil Degradation and MEL Production in a Yeast Strain, Pseudozyma tsukubaensis, by Translation Elongation Factor 1 Promoter-driven Expression of a Lipase

The basidiomycetous yeast Pseudozyma tsukubaensis produces a mannosylerythritol lipid (MEL) homologue, a diastereomer type of MEL-B, from olive oil. In a previous study, MEL-B production was increased by the overexpression of lipase PaLIPAp in P. tsukubaensis 1E5, through the enhancement of oil consumption. In the present study, RNA sequence analysis was used to identify a promoter able to induce high-level PaLIPA expression. The recombinant strain, expressing PaLIPA via the translation elongation factor 1 alpha/Tu promoter, showed higher lipase activity, rates of oil degradation, and MEL-B production than the strain which generated in our previous study.