Project description:Hyaluronic acid (HA) is a biopolymer formed by UDP-glucuronic acid and UDP-N-acetyl-glucosamine disaccharide units linked by β-1,4 and β-1,3 glycosidic bonds. It is widely employed in medical and cosmetic procedures. HA is synthesized by hyaluronan synthase (HAS), which catalyzes the precursors' ligation in the cytosol, elongates the polymer chain, and exports it to the extracellular space. Here, we engineer Ogataea (Hansenula) polymorpha for HA production by inserting the genes encoding UDP-glucose 6-dehydrogenase, for UDP-glucuronic acid production, and HAS. Two microbial HAS, from Streptococcus zooepidemicus (hasAs) and Pasteurella multocida (hasAp), were evaluated separately. Additionally, we assessed a genetic switch using integrases in O. polymorpha to uncouple HA production from growth. Four strains were constructed containing both has genes under the control of different promoters. In the strain containing the genetic switch, HA production was verified by a capsule-like layer around the cells by scanning electron microscopy in the first 24 h of cultivation. For the other strains, the HA was quantified only after 48 h and in an optimized medium, indicating that HA production in O. polymorpha is limited by cultivation conditions. Nevertheless, these results provide a proof-of-principle that O. polymorpha is a suitable host for HA production.
Project description:BackgroundOgataea polymorpha is a thermotolerant, methylotrophic yeast with significant industrial applications. While previously mainly used for protein synthesis, it also holds promise for producing platform chemicals. O. polymorpha has the distinct advantage of using methanol as a substrate, which could be potentially derived from carbon capture and utilization streams. Full development of the organism into a production strain and estimation of the metabolic capabilities require additional strain design, guided by metabolic modeling with a genome-scale metabolic model. However, to date, no genome-scale metabolic model is available for O. polymorpha.ResultsTo overcome this limitation, we used a published reconstruction of the closely related yeast Komagataella phaffii as a reference and corrected reactions based on KEGG and MGOB annotation. Additionally, we conducted phenotype microarray experiments to test the suitability of 190 substrates as carbon sources. Over three-quarter of the substrate use was correctly reproduced by the model and 27 new substrates were added, that were not present in the K. phaffii reference model.ConclusionThe developed genome-scale metabolic model of O. polymorpha will support the engineering of synthetic metabolic capabilities and enable the optimization of production processes, thereby supporting a sustainable future methanol economy.
Project description:Bio-manufacturing via microbial cell factory requires large promoter library for fine-tuned metabolic engineering. Ogataea polymorpha, one of the methylotrophic yeasts, possesses advantages in broad substrate spectrum, thermal-tolerance, and capacity to achieve high-density fermentation. However, a limited number of available promoters hinders the engineering of O. polymorpha for bio-productions. Here, we systematically characterized native promoters in O. polymorpha by both GFP fluorescence and fatty alcohol biosynthesis. Ten constitutive promoters (P PDH , P PYK , P FBA , P PGM , P GLK , P TRI , P GPI , P ADH1 , P TEF1 and P GCW14 ) were obtained with the activity range of 13%-130% of the common promoter P GAP (the promoter of glyceraldehyde-3-phosphate dehydrogenase), among which P PDH and P GCW14 were further verified by biosynthesis of fatty alcohol. Furthermore, the inducible promoters, including ethanol-induced P ICL1 , rhamnose-induced P LRA3 and P LRA4 , and a bidirectional promoter (P Mal -P Per ) that is strongly induced by sucrose, further expanded the promoter toolbox in O. polymorpha. Finally, a series of hybrid promoters were constructed via engineering upstream activation sequence (UAS), which increased the activity of native promoter P LRA3 by 4.7-10.4 times without obvious leakage expression. Therefore, this study provided a group of constitutive, inducible, and hybrid promoters for metabolic engineering of O. polymorpha, and also a feasible strategy for rationally regulating the promoter strength.
Project description:Methylotrophic yeast Ogataea polymorpha is capable to utilize multiple carbon feedstocks especially methanol as sole carbon source and energy, making it an ideal host for bio-manufacturing. However, the lack of gene integration sites limits its systems metabolic engineering, in particular construction of genome-integrated pathway. We here screened the genomic neutral sites for gene integration without affecting cellular fitness, by genomic integration of an enhanced green fluorescent protein (eGFP) gene via CRISPR-Cas9 technique. After profiling the growth and fluorescent intensity in various media, 17 genome positions were finally identified as potential neutral sites. Finally, integration of fatty alcohol synthetic pathway genes into neutral sites NS2 and NS3, enabled the production of 4.5 mg/L fatty alcohols, indicating that these neutral sites can be used for streamline metabolic engineering in O. polymorpha. We can anticipate that the neutral sites screening method described here can be easily adopted to other eukaryotes.
Project description:The methylotrophic yeast Ogataea polymorpha has long been a useful system for recombinant protein production, as well as a model system for methanol metabolism, peroxisome biogenesis, thermotolerance, and nitrate assimilation. It has more recently become an important model for the evolution of mating-type switching. Here, we present a population genomics analysis of 47 isolates within the O. polymorpha species complex, including representatives of the species O. polymorpha, Ogataea parapolymorpha, Ogataea haglerorum, and Ogataea angusta. We found low levels of nucleotide sequence diversity within the O. polymorpha species complex and identified chromosomal rearrangements both within and between species. In addition, we found that one isolate is an interspecies hybrid between O. polymorpha and O. parapolymorpha and present evidence for loss of heterozygosity following hybridization.
Project description:Methanol biotransformation can expand biorefinery substrate spectrum other than biomass by using methylotrophic microbes. Ogataea (Hansenula) polymorpha, a representative methylotrophic yeast, attracts much attention due to its thermotolerance, but the low homologous recombination (HR) efficiency hinders its precise genetic manipulation during cell factory construction. Here, recombination machinery engineering (rME) is explored for enhancing HR activity together with establishing an efficient CRISPR-Cas9 system in O. polymorpha. Overexpression of HR-related proteins and down-regulation of non-homologous end joining (NHEJ) increased HR rates from 20%-30% to 60%-70%. With these recombination perturbation mutants, a competition between HR and NHEJ is observed. This HR up-regulated system has been applied for homologous integration of large fragments and in vivo assembly of multiple fragments, which enables the production of fatty alcohols in O. polymorpha. These findings will simplify genetic engineering in non-conventional yeasts and facilitate the adoption of O. polymorpha as an attractive cell factory for industrial application.