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Samer Younes,Dania Awad,Elias Kassab,Martina Haack,Claudia Schuler,Norbert Mehlmer,Thomas Brueck 한국생물공학회 2021 Biotechnology and Bioprocess Engineering Vol.26 No.4
The monomer, 3-hydroxybutyrate (3HB), plays an interesting role as a precursor for antibiotics, vitamins, and bioplastics such as polyhydroxybutyrates (PHB). The biotechnological production of both compounds in Escherichia coli has seen increased interest in the last decade. The central metabolite in the 3HB production pathway is acetyl-CoA, the derivative of coenzyme A (CoA). Enriching the intracellular pool of these cofactors could improve 3HB titers. In our study, we opted to increase CoA titers by upregulating pantothenate kinase (PanK), the rate limiting step in CoA biosynthetic pathway. To this end, 4 PanKs genes of different taxonomic origins (mammalian, fungal, and bacterial) were individually expressed and evaluated in 3HB producing E. coli cells. In shake flask studies, strains expressing Aspergillus nidulans PankII and Mus musculus PanK1β achieved the highest 3HB titers. In a bioreactor fermentation, the strain harboring murine PanK1β resulted in 7.6 g/L compared to 5.4 g/L of 3HB in the control strain. Although structurally different from the bacterial PankI, our study showed that eukaryotic Panks can supplement the kinase activity in prokaryotes. Expressing the exogenous PanKs offer several advantages over the host’s enzyme; PanKII is only inhibited by acetyl- CoA, for which the 3HB-production system would provide a constant metabolic sink. Additionally, PanK1β is weakly regulated by acetyl-CoA, and its activity is stimulated by free CoA. Overexpressing eukaryotic PanKs constitutes a suitable strategy for improving 3HB titers in E. coli.
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Phenotypic and Cell Wall Proteomic Characterization of a DDR48 Mutant Candida albicans Strain
( Pamela El Khoury ),( Carell Salameh ),( Samer Younes ),( Andy Awad ),( Yana Said ),( Roy A. Khalaf ) 한국미생물 · 생명공학회 2019 Journal of microbiology and biotechnology Vol.29 No.11
Candida albicans is an opportunistic fungus possessing multiple virulence factors controlling pathogenicity. Cell wall proteins are the most important among these factors, being the first elements contacting the host. Ddr48 is a cell wall protein consisting of 212 amino acids. A DDR48 haploinsufficient mutant strain was previously found necessary for proper oxidative stress response and drug resistance. In this study, we aimed to further elucidate the role of Ddr48 by performing additional phenotypic characterization assays. A combinatory proteomic and bioinformatics approach was also undertaken to determine differentially expressed cell wall proteins. Results showed that the mutant strain exhibited a 10% decrease in adhesion mirrored by a 20% decrease in biofilm formation, and slight sensitivity to menadione, diamide, and SDS. Both strains showed similar hyphae formation, virulence, temperature tolerance, and calcofluor white and Congo red sensitivities. Furthermore, a total of 8 and 10 proteins were identified exclusively in the wild-type strain grown under filamentous and nonfilamentous conditions respectively. Results included proteins responsible for superoxide stress resistance (Sod4 and Sod6), adhesion (Als3, Hyr4, Pmt1, and Utr2), biofilm formation (Hsp90, Ece1, Rim9, Ipp1, and Pra1) and cell wall integrity (Utr2 and Pga4). The lack of detection of these proteins in the mutant strain correlates with the observed phenotypes.
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