ORCID Profile
0000-0003-2428-5509
Current Organisation
Queensland University of Technology
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Microeconomic Theory | Experimental Economics | Applied Economics
Market-Based Mechanisms | Microeconomics not elsewhere classified |
Publisher: Springer Science and Business Media LLC
Date: 07-01-2021
DOI: 10.1186/S12934-020-01499-7
Abstract: Pichia pastoris ( Komagataella phaffii ) is an important platform for heterologous protein production due to its growth to high cell density and outstanding secretory capabilities. Recent developments in synthetic biology have extended the toolbox for genetic engineering of P. pastoris to improve production strains. Yet, overloading the folding and secretion capacity of the cell by over-expression of recombinant proteins is still an issue and rational design of strains is critical to achieve cost-effective industrial manufacture. Several enzymes are commercially produced in P. pastoris , with phytases being one of the biggest on the global market. Phytases are ubiquitously used as a dietary supplement for swine and poultry to increase digestibility of phytic acid, the main form of phosphorous storage in grains. Potential bottlenecks for expression of E. coli AppA phytase in P. pastoris were explored by applying bidirectional promoters (BDPs) to express AppA together with folding chaperones, disulfide bond isomerases, trafficking proteins and a cytosolic redox metabolism protein. Additionally, transcriptional studies were used to provide insights into the expression profile of BDPs. A flavoprotein encoded by ERV2 that has not been characterised in P. pastoris was used to improve the expression of the phytase, indicating its role as an alternative pathway to ERO1 . Subsequent AppA production increased by 2.90-fold compared to the expression from the state of the AOX1 promoter. The microbial production of important industrial enzymes in recombinant systems can be improved by applying newly available molecular tools. Overall, the work presented here on the optimisation of phytase production in P. pastoris contributes to the improved understanding of recombinant protein folding and secretion in this important yeast microbial production host.
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.JBIOTEC.2022.04.001
Abstract: Astaxanthin (AX) is a potent antioxidant with increasing biotechnological and commercial potential as a feed supplement, and gives salmonids and crustaceans their attractive characteristic pink color. The red yeast Phaffia rhodozyma naturally produces AX as its main fermentation product but wild-type strains and those previously generated through classical random mutagenesis produce low yields of AX. Existing strains do not meet commercial economic requirements, fundamentally due to a lack of understanding of the underlying mechanisms and genotype-phenotype associations regarding AX production in P. rhodozyma. In the present study, screening of P. rhodozyma CBS 6938 mutant strains generated through chemical and ultra violet radiation mutagenesis delivered increased AX production yields that were then maximized using culture media optimization and fed-batch culture kinetic modeling. The whole genomes of the wild-type and eight increased production strains were sequenced to identify genomic changes. The selected strains produced 50-fold more AX than the wild-type strain with a total biomass of around 100 gDCW/L and a carotenoid production of 1 g/L. Genomic variant analyses found 368 conserved mutations across the selected strains with important mutations found in protein coding regions associated with regulators and catalysts of AX precursors in the mevalonate pathway, the electron transport chain, oxidative stress mechanisms, and carotenogenesis.
Publisher: Authorea, Inc.
Date: 10-05-2022
DOI: 10.22541/AU.165218774.43718228/V1
Abstract: Astaxanthin (AX) is a carotenoid pigment with antioxidant properties. AX is used widely in the animal feed industry as a supplement. Wild-type strains of Phaffia rhodozyma naturally produce low AX yields, but we increased AX yields 50-fold in previous research using random mutagenesis of P. rhodozyma CBS6938 and fermentation optimisation. Genome sequencing linked phenotype and genome changes of the increased AX production but relevant metabolic changes were not resolved. In this study, the wild-type and the superior P. rhodozyma mutant strains were grown in chemically defined media and instrumented fermenters. Differential kinetic, metabolomics, and transcriptomics data were collected. Our results suggest that carotenoid production was mainly associated with cell growth and had a positive regulation of central carbon metabolism metabolites associated with glycolysis, the pentose phosphate pathway, the TCA cycle, and amino acids and fatty acids biosynthesis. In the stationary phase, amino acids associated with the TCA cycle increased, but most of the fatty acids and central carbon metabolism metabolites decreased. TCA cycle metabolites such as succinate, fumarate, and α-ketoglutarate were in abundance during both growth and stationary phases. The overall observed metabolic changes in the central carbon metabolism and abundance of TCA cycle metabolites suggest an improvement in the electron transport chain and the provision of the electrons required for the AX synthesis. Transcriptomic data correlated with the metabolic data and found a positive regulation of genes associated with the electron respiratory chain suggesting this to be the main driver for improved AX production in the mutant strain.
Publisher: Elsevier BV
Date: 12-2010
Publisher: American Society for Microbiology
Date: 30-06-2016
Abstract: Propionibacterium acidipropionici produces propionic acid as its main fermentation product. Traditionally derived from fossil fuels, environmental and sustainable issues have revived the interest in producing propionic acid using biological resources. Here, we present the closed sequence of Propionibacterium acidipropionici ATCC 55737, an efficient propionic acid producer.
Publisher: Wiley
Date: 27-01-2023
DOI: 10.1002/BIT.28332
Abstract: Astaxanthin (AX) is a carotenoid pigment with antioxidant properties widely used as a feed supplement. Wild‐type strains of Phaffia rhodozyma naturally produce low AX yields, but we increased AX yields 50‐fold in previous research using random mutagenesis of P. rhodozyma CBS6938 and fermentation optimization. On that study, genome changes were linked with phenotype, but relevant metabolic changes were not resolved. In this study, the wild‐type and the superior P. rhodozyma mutant strains were grown in chemically defined media and instrumented fermenters. Differential kinetic, metabolomics, and transcriptomics data were collected. Our results suggest that carotenoid production was mainly associated with cell growth and had a positive regulation of central carbon metabolism metabolites, amino acids, and fatty acids. In the stationary phase, amino acids associated with the TCA cycle increased, but most of the fatty acids and central carbon metabolism metabolites decreased. TCA cycle metabolites were in abundance and media supplementation of citrate, malate, α‐ketoglutarate, succinate, or fumarate increased AX production in the mutant strain. Transcriptomic data correlated with the metabolic and genomic data and found a positive regulation of genes associated with the electron transport chain suggesting this to be the main driver for improved AX production in the mutant strain.
Publisher: Oxford University Press (OUP)
Date: 22-02-2023
DOI: 10.1093/BIB/BBAD062
Abstract: Cell-state transition can reveal additional information from single-cell ribonucleic acid (RNA)-sequencing data in time-resolved biological phenomena. However, most of the current methods are based on the time derivative of the gene expression state, which restricts them to the short-term evolution of cell states. Here, we present single-cell State Transition Across-s les of RNA-seq data (scSTAR), which overcomes this limitation by constructing a paired-cell projection between biological conditions with an arbitrary time span by maximizing the covariance between two feature spaces using partial least square and minimum squared error methods. In mouse ageing data, the response to stress in CD4+ memory T cell subtypes was found to be associated with ageing. A novel Treg subtype characterized by mTORC activation was identified to be associated with antitumour immune suppression, which was confirmed by immunofluorescence microscopy and survival analysis in 11 cancers from The Cancer Genome Atlas Program. On melanoma data, scSTAR improved immunotherapy-response prediction accuracy from 0.8 to 0.96.
Publisher: Wiley
Date: 25-07-2023
DOI: 10.1002/BIT.28510
Abstract: Pichia pastoris ( Komagataella phaffii ) is a fast‐growing methylotrophic yeast with the ability to assimilate several carbon sources such as methanol, glucose, or glycerol. It has been shown to have outstanding secretion capability with a variety of heterologous proteins. In previous studies, we engineered P. pastoris to co‐express Escherichia coli AppA phytase and the HAC1 transcriptional activator using a bidirectional promoter. Phytase production was characterized in shake flasks and did not reflect industrial conditions. In the present study, phytase expression was explored and optimized using instrumented fermenters in continuous and fed‐batch modes. First, the production of phytase was investigated under glucose de‐repression in continuous culture at three dilution factors, 0.5 d −1 , 1 d −1 , and 1.5 d −1 . The fermenter parameters of these cultures were used to inform a kinetic model in batch and fed‐batch modes for growth and phytase production. The kinetic model developed aided to design the glucose‐feeding profile of a fed‐batch culture. Kinetic model simulations under glucose de‐repression and fed‐batch conditions identified optimal phytase productivity at the specific growth rate of 0.041 h −1 . Validation of the model simulation with experimental data confirmed the feasibility of the model to predict phytase production in our newly engineered strain. Methanol was used only to induce the expression of phytase at high cell densities. Our results showed that high phytase production required two stages, the first stage used glucose under de‐repression conditions to generate biomass while expressing phytase, and stage two used methanol to induce phytase expression. The production of phytase was improved 3.5‐fold by methanol induction compared to the expression with glucose alone under de‐repression conditions to a final phytase activity of 12.65 MU/L. This final volumetric phytase production represented an approximate 36‐fold change compared to the flask fermentations. Finally, the phytase protein produced was assayed to confirm its molecular weight, and pH and temperature profiles. This study highlights the importance of optimizing protein production in P. pastoris when using novel promoters and presents a general approach to performing bioprocess optimization in this important production host.
Publisher: Wiley
Date: 20-10-2017
Abstract: Traditionally derived from fossil fuels, biological production of propionic acid has recently gained interest. Propionibacterium species produce propionic acid as their main fermentation product. Production of other organic acids reduces propionic acid yield and productivity, pointing to by-products gene-knockout strategies as a logical solution to increase yield. However, removing by-product formation has seen limited success due to our inability to genetically engineer the best producing strains (i.e. Propionibacterium acidipropionici). To overcome this limitation, random mutagenesis continues to be the best path towards improving strains for biological propionic acid production. Recent advances in next generation sequencing opened new avenues to understand improved strains. In this work, we use genome shuffling on two wild type strains to generate a better propionic acid producing strain. Using next generation sequencing, we mapped the genomic changes leading to the improved phenotype. The best strain produced 25% more propionic acid than the wild type strain. Sequencing of the strains showed that genomic changes were restricted to single point mutations and gene duplications in well-conserved regions in the genomes. Such results confirm the involvement of gene conversion in genome shuffling as opposed to long genomic insertions.
Publisher: Springer Science and Business Media LLC
Date: 31-03-2021
DOI: 10.1186/S13068-021-01936-8
Abstract: Phytases are widely used commercially as dietary supplements for swine and poultry to increase the digestibility of phytic acid. Enzyme development has focused on increasing thermostability to withstand the high temperatures during industrial steam pelleting. Increasing thermostability often reduces activity at gut temperatures and there remains a demand for improved phyases for a growing market. In this work, we present a thermostable variant of the E. coli AppA phytase, ApV1, that contains an extra non-consecutive disulfide bond. Detailed biochemical characterisation of ApV1 showed similar activity to the wild type, with no statistical differences in k cat and K M for phytic acid or in the pH and temperature activity optima. Yet, it retained approximately 50% activity after incubations for 20 min at 65, 75 and 85 °C compared to almost full inactivation of the wild-type enzyme. Production of ApV1 in Pichia pastoris ( Komagataella phaffi ) was much lower than the wild-type enzyme due to the presence of the extra non-consecutive disulfide bond. Production bottlenecks were explored using bidirectional promoters for co-expression of folding chaperones. Co-expression of protein disulfide bond isomerase (Pdi) increased production of ApV1 by ~ 12-fold compared to expression without this folding catalyst and restored yields to similar levels seen with the wild-type enzyme . Overall, the results show that protein engineering for enhanced enzymatic properties like thermostability may result in folding complexity and decreased production in microbial systems. Hence parallel development of improved production strains is imperative to achieve the desirable levels of recombinant protein for industrial processes .
Publisher: Authorea, Inc.
Date: 18-07-2022
DOI: 10.22541/AU.165816380.04897659/V1
Abstract: Pichia pastoris ( Komagataella phaffii ) is a fast-growing methylotrophic yeast with the ability to assimilate several carbon sources such as methanol, glucose, or glycerol. It has been shown to have outstanding secretion capability with a variety of heterologous proteins. In previous studies, we engineered P. pastoris to co-express E. coli AppA phytase and the HAC1 transcriptional activator using a bidirectional promoter. Phytase production was characterised in shake flasks and did not reflect industrial conditions. In the present study, phytase expression was explored and optimised using instrumented fermenters in continuous and fed-batch modes. First, the production of phytase was investigated under glucose de-repression in continuous culture at three dilution factors, 0.5 d , 1 d , and 1.5 d . The fermenter parameters of these cultures were used to inform a kinetic model in batch and fed-batch modes for growth and phytase production. The kinetic model developed aided to design the glucose feeding profile of a fed-batch culture. Kinetic model simulations under glucose de-repression and fed-batch conditions identified an optimal phytase productivity at the specific growth rate of 0.041 h . Validation of the model simulation with experimental data confirmed the feasibility of the model to predict phytase production in our newly engineered strain. Methanol was used only to induce the expression of phytase at high cell densities. Our results showed that high phytase production required two stages, the first stage used glucose under de-repression conditions to generate biomass while expressing phytase, and stage two used methanol to induce phytase expression. The production of phytase was improved 3.5-fold by methanol induction compared to the expression with glucose alone under de-repression conditions to a final phytase activity of 12.65 MU/L. This final volumetric phytase production represented an approximate 36-fold change compared to the flask fermentations. This two-phase strategy allowed to optimise phytase productivity by producing phytase during both growth and methanol induction phases. Finally, the phytase protein produced was assayed to confirm its molecular weight, and pH and temperature profiles. This study highlights the importance of optimising protein production in P. pastoris when using novel promoters and presents a general approach to performing bioprocess optimisation in this important production host.
Publisher: Springer Science and Business Media LLC
Date: 13-08-2018
Start Date: 06-2014
End Date: 06-2017
Amount: $349,785.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2019
End Date: 2022
Funder: Advance Queensland
View Funded ActivityStart Date: 2003
End Date: 2006
Funder: Consejo Nacional de Ciencia y Tecnología
View Funded ActivityStart Date: 2017
End Date: 2018
Funder: Advance Queensland
View Funded Activity