Production of recombinant human lysosomal acid lipase in Schizosaccharomyces pombe: development of a fed-batch fermentation and purification process

A convenient new method for reproducible fed-batch fermentation of fission yeast Schizosaccharomyces pombe

OBJECTIVES

Development of an open-loop fed-batch protocol for highly reproducible fermentation of fission yeast that starts from batch cultures instead of glucose-limited aerobic chemostat cultures.

RESULTS

A new strategy was employed that consists of an exponential feeding phase followed by a starvation period and then a linear feeding phase. A comparison of several independent fed-batch fermentations of a recombinant fission yeast strain showed that while during the initial phase process parameters such as glucose consumption and CO₂ evolution varied considerably as expected, they were much more uniform during the third phase. For instance, the normalized standard deviation of glucose consumption was thirty times higher during the exponential feeding phase of the fermentation that during the linear feeding phase.

CONCLUSION

These data demonstrate the usefulness of the proposed strategy. It is expected that by variation of only two parameters (the total amount of glucose fed in the initial phase and the time frame of the starvation phase) the protocol can easily be adapted to other microbes.

Engineering and modification of microbial chassis for systems and synthetic biology

Engineering and modifying synthetic microbial chassis is one of the best ways not only to unravel the fundamental principles of life but also to enhance applications in the health, medicine, agricultural, veterinary, and food industries. The two primary strategies for constructing a microbial chassis are the top-down approach (genome reduction) and the bottom-up approach (genome synthesis). Research programs on this topic have been funded in several countries. The 'Minimum genome factory' (MGF) project was launched in 2001 in Japan with the goal of constructing microorganisms with smaller genomes for industrial use. One of the best examples of the results of this project is E. coli MGF-01, which has a reduced-genome size and exhibits better growth and higher threonine production characteristics than the parental strain [1]. The 'cell factory' project was carried out from 1998 to 2002 in the Fifth Framework Program of the EU (European Union), which tried to comprehensively understand microorganisms used in the application field. One of the outstanding results of this project was the elucidation of proteins secreted by Bacillus subtilis, which was summarized as the 'secretome' [2]. The GTL (Genomes to Life) program began in 2002 in the United States. In this program, researchers aimed to create artificial cells both in silico and in vitro, such as the successful design and synthesis of a minimal bacterial genome by John Craig Venter's group [3]. This review provides an update on recent advances in engineering, modification and application of synthetic microbial chassis, with particular emphasis on the value of learning about chassis as a way to better understand life and improve applications.

Lysosomal enzyme replacement therapies: Historical development, clinical outcomes, and future perspectives

Lysosomes and lysosomal enzymes play a central role in numerous cellular processes, including cellular nutrition, recycling, signaling, defense, and cell death. Genetic deficiencies of lysosomal components, most commonly enzymes, are known as "lysosomal storage disorders" or "lysosomal diseases" (LDs) and lead to lysosomal dysfunction. LDs broadly affect peripheral organs and the central nervous system (CNS), debilitating patients and frequently causing fatality. Among other approaches, enzyme replacement therapy (ERT) has advanced to the clinic and represents a beneficial strategy for 8 out of the 50-60 known LDs. However, despite its value, current ERT suffers from several shortcomings, including various side effects, development of "resistance", and suboptimal delivery throughout the body, particularly to the CNS, lowering the therapeutic outcome and precluding the use of this strategy for a majority of LDs. This review offers an overview of the biomedical causes of LDs, their socio-medical relevance, treatment modalities and caveats, experimental alternatives, and future treatment perspectives.

Human recombinant lysosomal enzymes produced in microorganisms

Lysosomal storage diseases (LSDs) are caused by accumulation of partially degraded substrates within the lysosome, as a result of a function loss of a lysosomal protein. Recombinant lysosomal proteins are usually produced in mammalian cells, based on their capacity to carry out post-translational modifications similar to those observed in human native proteins. However, during the last years, a growing number of studies have shown the possibility to produce active forms of lysosomal proteins in other expression systems, such as plants and microorganisms. In this paper, we review the production and characterization of human lysosomal proteins, deficient in several LSDs, which have been produced in microorganisms. For this purpose, Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, Yarrowia lipolytica, and Ogataea minuta have been used as expression systems. The recombinant lysosomal proteins expressed in these hosts have shown similar substrate specificities, and temperature and pH stability profiles to those produced in mammalian cells. In addition, pre-clinical results have shown that recombinant lysosomal enzymes produced in microorganisms can be taken-up by cells and reduce the substrate accumulated within the lysosome. Recently, metabolic engineering in yeasts has allowed the production of lysosomal enzymes with tailored N-glycosylations, while progresses in E. coli N-glycosylations offer a potential platform to improve the production of these recombinant lysosomal enzymes. In summary, microorganisms represent convenient platform for the production of recombinant lysosomal proteins for biochemical and physicochemical characterization, as well as for the development of ERT for LSD.

Improving industrial yeast strains: exploiting natural and artificial diversity

Yeasts have been used for thousands of years to make fermented foods and beverages, such as beer, wine, sake, and bread. However, the choice for a particular yeast strain or species for a specific industrial application is often based on historical, rather than scientific grounds. Moreover, new biotechnological yeast applications, such as the production of second-generation biofuels, confront yeast with environments and challenges that differ from those encountered in traditional food fermentations. Together, this implies that there are interesting opportunities to isolate or generate yeast variants that perform better than the currently used strains. Here, we discuss the different strategies of strain selection and improvement available for both conventional and nonconventional yeasts. Exploiting the existing natural diversity and using techniques such as mutagenesis, protoplast fusion, breeding, genome shuffling and directed evolution to generate artificial diversity, or the use of genetic modification strategies to alter traits in a more targeted way, have led to the selection of superior industrial yeasts. Furthermore, recent technological advances allowed the development of high-throughput techniques, such as 'global transcription machinery engineering' (gTME), to induce genetic variation, providing a new source of yeast genetic diversity.

Engineered high content of ricinoleic acid in fission yeast Schizosaccharomyces pombe

In an effort to produce ricinoleic acid (12-hydroxy-octadeca-cis-9-enoic acid: C18:1-OH) as a petrochemical replacement in a variety of industrial processes, we introduced Claviceps purpurea oleate ∆12-hydroxylase gene (CpFAH12) to Schizosaccharomyces pombe, putting it under the control of inducible nmt1 promoter. Since Fah12p is able to convert oleic acid to ricinoleic acid, we thought that S. pombe, in which around 75% of total fatty acid (FA) is oleic acid, would accordingly be an ideal microorganism for high production of ricinoleic acid. Unfortunately, at the normal growth temperature of 30 °C, S. pombe cells harboring CpFAH12 grew poorly when the CpFAH12 gene expression was induced, perhaps implicating ricinoleic acid as toxic in S. pombe. However, in line with a likely thermoinstability of Fah12p, there was almost no growth inhibition at 37 °C or, by contrast with 30 °C and lower temperatures, ricinoleic acid accumulation. Accordingly, various optimization steps led to a regime with preliminary growth at 37 °C followed by a 5-day incubation at 20 °C, and the level of ricinoleic acid reached 137.4 μg/ml of culture that corresponded to 52.6% of total FA.

Overview of fungal lipase: a review

Lipases (triacylglycerolacyl hydrolases, EC3.1.1.3) are class of enzymes which catalyze the hydrolysis of long-chain triglycerides. In this review paper, an overview regarding the fungal lipase production, purification, and application is discussed. The review describes various industrial applications of lipase in pulp and paper, food, detergent, and textile industries. Some important lipase-producing fungal genera include Aspergillus, Penicillium, Rhizopus, Candida, etc. Current fermentation process techniques such as batch, fed-batch, and continuous mode of lipase production in submerged and solid-state fermentations are discussed in details. The purification of lipase by hydrophobic interaction chromatography is also discussed. The development of mathematical models applied to lipase production is discussed with special emphasis on lipase engineering.

Enhanced protein secretion from multiprotease-deficient fission yeast by modification of its vacuolar protein sorting pathway

Previously, we achieved approximately 30-fold enhanced secretion of the protease-sensitive model protein human growth hormone (hGH) by multiple gene deletion of seven obstructive proteases in the fission yeast Schizosaccharomyces pombe. However, intracellular retention of secretory hGH was found in the resultant multiprotease-deficient strains. As a solution, genetic modification of the intracellular trafficking pathway that is related to intracellular retention of hGH was attempted on a protease octuple deletant strain. Vacuolar accumulation of the intracellularly retained hGH was identified by secretory expression of hGH fused with EGFP, and three vacuolar protein sorting (vps)-deficient strains, vps10Delta, vps22Delta, and vps34Delta, were determined on account of their hGH secretion efficiency. The mutant vps10Delta was found to be effective for hGH secretion, which suggested a role for vps10 in the vacuolar accumulation of the intracellularly retained hGH. Finally, vps10 deletion was performed on the protease octuple deletant strain, which led to an approximately 2-fold increase in hGH secretion. This indicated the possible application of secretory-pathway modification and multiple protease deletion for improving heterologous protein secretion from the fission yeast S. pombe.

Production of heterologous proteins using the fission-yeast (Schizosaccharomyces pombe) expression system

The fission yeast Schizosaccharomyces pombe is a particularly useful model for studying the function and regulation of genes from higher eukaryotes. The genome of Sc. pombe has been sequenced, and DNA microarray, proteome and transcriptome analyses have been carried out. Among the well-characterized yeast species, Sc. pombe is considered an attractive host for the production of heterologous proteins. Expression vectors for high-level expression in Sc. pombe have been developed and many foreign proteins have been successfully expressed. However, further improvements in the protein-expressing host systems are still required for the production of heterologous proteins involved in post-translational modification, metabolism and intracellular trafficking. This minireview focuses on recent advances in heterologous protein production by use of engineered fission-yeast strains.

Enhanced productivity of protease-sensitive heterologous proteins by disruption of multiple protease genes in the fission yeast Schizosaccharomyces pombe

The creation of protease-deficient mutants to avoid product degradation is one of the current strategies employed to improve productivity and secretion efficiency of heterologous protein expression. We previously constructed a set of single protease-deficient mutants of the fission yeast Schizosaccharomyces pombe by respective disruption of 52 protease genes, and we succeeded in confirming useful disruptants (Idiris et al., Yeast 23:83-99, 2006). In the present study, we attempted multiple deletions of 13 protease genes, single deletions of which were previously confirmed as being beneficial for reducing extracellular product degradation. Using PCR-based gene replacement, a series of multiple deletion strains was constructed by multiple disruption of a maximum of seven protease genes. Effects of the resultant multiple deletion strains on heterologous expression were then measured by practical expression of a proteolytically sensitive model protein, the human growth hormone (hGH). Time profiles of hGH secretion from each resultant mutant demonstrated significantly enhanced hGH productivity with processing of the multiple protease deletions. The data clearly indicated that disruption of multiple protease genes in the fission yeast is an effective method for controlling proteolytic degradation of heterologous proteins particularly susceptible to proteases.

Construction of a protease-deficient strain set for the fission yeast Schizosaccharomyces pombe, useful for effective production of protease-sensitive heterologous proteins

One of the major problems hindering effective production and purification of heterologous proteins from the fission yeast Schizosaccharomyces pombe is proteolytic degradation of the recombinant gene products by host-specific proteases. As an initial solution to this problem, we constructed a protease-deficient disruptant set by respective disruption of 52 Sz. pombe protease genes. Functional screening of the resultant set was performed by observing secretory production of a proteolytically sensitive model protein, human growth hormone (hGH). The results indicated that some of the resultant disruptants were effective in reducing hGH degradation, as observed during the hGH expression procedure and mainly as a result of unknown serine- and/or cysteine-type proteases in the culture medium. These findings also demonstrated that construction of a protease-deficient strain set is not only useful for practical application in protein production, but also for functional screening, specification and modification of proteases in Sz. pombe, where further investigations of proteolytic processes and improvement through multiple gene manipulations are required.