Reinvestigation of Coenzyme Q10 Isolation from Sporidiobolus johnsonii

Production of Coenzyme Q10 by microbes: an update

Coenzyme Q₁₀ (CoQ₁₀) is the main CoQ species in human and is used extensively in food, cosmetic and medicine industries because of its antioxidant properties and its benefit in prophylactic medicine and therapy for a variety of diseases. Among various approaches to increase the production of CoQ₁₀, microbial fermentation is the most effective. As knowledge of the biosynthetic enzymes and regulatory mechanisms modulating CoQ₁₀ production increases, opportunities arise for metabolic engineering of CoQ₁₀ in microbial hosts. In this review, we present various strategies used up to date to improve CoQ₁₀ production and focus on metabolic engineering of CoQ₁₀ overproduction in microbes. General strategies of metabolic engineering include providing sufficient precursors for CoQ₁₀, increasing metabolic fluxes, and expanding storage capacity for CoQ₁₀. Based on these strategies, CoQ₁₀ production has been significantly improved in natural CoQ₁₀ producers, as well as in heterologous hosts.

Phosphate limitation increases coenzyme Q10 production in industrial Rhodobacter sphaeroides HY01

Coenzyme Q₁₀ (CoQ₁₀) is an important component of the respiratory chain in humans and some bacteria. As a high-value-added nutraceutical antioxidant, CoQ₁₀ has excellent capacity to prevent cardiovascular disease. The content of CoQ₁₀ in the industrial Rhodobacter sphaeroides HY01 is hundreds of folds higher than normal physiological levels. In this study, we found that overexpression or optimization of the synthetic pathway failed CoQ₁₀ overproduction in the HY01 strain. Moreover, under phosphate- limited conditions (decreased phosphate or in the absence of inorganic phosphate addition), CoQ₁₀ production increased significantly by 12% to220 mg/L, biomass decreased by 12%, and the CoQ₁₀ productivity of unit cells increased by 27%. In subsequent fed-batch fermentation, CoQ₁₀ production reached 272 mg/L in the shake-flask fermentation and 1.95 g/L in a 100-L bioreactor under phosphate limitation. Furthermore, to understand the mechanism associated with CoQ₁₀ overproduction under phosphate- limited conditions, the comparatve transcriptome analysis was performed. These results indicated that phosphate limitation combined with glucose fed-batch fermentation represented an effective strategy for CoQ₁₀ production in the HY01. Phosphate limitation induced a pleiotropic effect on cell metabolism, and that improved CoQ₁₀ biosynthesis efficiency was possibly related to the disturbance of energy metabolism and redox potential.

Cellular factories for coenzyme Q10 production

Coenzyme Q₁₀ (CoQ₁₀), a benzoquinone present in most organisms, plays an important role in the electron-transport chain, and its deficiency is associated with various neuropathies and muscular disorders. CoQ₁₀ is the only lipid-soluble antioxidant found in humans, and for this, it is gaining popularity in the cosmetic and healthcare industries. To meet the growing demand for CoQ₁₀, there has been considerable interest in ways to enhance its production, the most effective of which remains microbial fermentation. Previous attempts to increase CoQ₁₀ production to an industrial scale have thus far conformed to the strategies used in typical metabolic engineering endeavors. However, the emergence of new tools in the expanding field of synthetic biology has provided a suite of possibilities that extend beyond the traditional modes of metabolic engineering. In this review, we cover the various strategies currently undertaken to upscale CoQ₁₀ production, and discuss some of the potential novel areas for future research.

Molecular, Physiological and Phenotypic Characterization of Paracoccus denitrificans ATCC 19367 Mutant Strain P-87 Producing Improved Coenzyme Q10

Coenzyme Q10 (CoQ10) is a blockbuster nutraceutical molecule which is often used as an oral supplement in the supportive therapy for cardiovascular diseases, cancer and neurodegenerative diseases. It is commercially produced by fermentation process, hence constructing the high yielding CoQ10 producing strains is a pre-requisite for cost effective production. Paracoccus denitrificans ATCC 19367, a biochemically versatile organism was selected to carry out the studies on CoQ10 yield improvement. The wild type strain was subjected to iterative rounds of mutagenesis using gamma rays and NTG, followed by selection on various inhibitors like CoQ10 structural analogues and antibiotics. The screening of mutants were carried out using cane molasses based optimized medium with feeding strategies at shake flask level. In the course of study, the mutant P-87 having marked resistance to gentamicin showed 1.25-fold improvements in specific CoQ10 content which was highest among all tested mutant strains. P-87 was phenotypically differentiated from the wild type strain on the basis of carbohydrate assimilation and FAME profile. Molecular differentiation technique based on AFLP profile showed intra specific polymorphism between wild type strain and P-87. This study demonstrated the beneficial outcome of induced mutations leading to gentamicin resistance for improvement of CoQ10 production in P. denitrificans mutant strain P-87. To investigate the cause of gentamicin resistance, rpIF gene from P-87 and wild type was sequenced. No mutations were detected on the rpIF partial sequence of P-87; hence gentamicin resistance in P-87 could not be conferred with rpIF gene. However, detecting the mutations responsible for gentamicin resistance in P-87 and correlating its role in CoQ10 overproduction is essential. Although only 1.25-fold improvement in specific CoQ10 content was achieved through mutant P-87, this mutant showed very interesting characteristic, differentiating it from its wild type parent strain P. denitrificans ATCC 19367, which are presented in this paper.

Morphological and Molecular Differentiation of Sporidiobolus johnsonii ATCC 20490 and Its Coenzyme Q10 Overproducing Mutant Strain UF16

Coenzyme Q10 (CoQ10) is an industrially important molecule having nutraceutical and cosmeceutical applications. CoQ10 is mainly produced by microbial fermentation and the process demands the use of strains with high productivity and yields of CoQ10. During strain improvement program consisting of sequential induced mutagenesis, rational selection and screening process, a mutant strain UF16 was generated from Sporidiobolus johnsonii ATCC 20490 with 2.3-fold improvements in CoQ10 content. EMS and UV rays were used as mutagenic agents for generating UF16 and it was rationally selected based on atorvastatin resistance as well as survival at free radicals exposure. We investigated the genotypic and phenotypic changes in UF16 in order to differentiate it from wild type strain. Morphologically it was distinct due to reduced pigmentation of colony, reduced cell size and significant reduction in mycelial growth forms with abundance of yeast forms. At molecular level, UF16 was differentiated based on PCR fingerprinting method of RAPD as well as large and small-subunit rRNA gene sequences. Rapid molecular technique of RAPD analysis using six primers showed 34 % polymorphic fragments with mean genetic distance of 0.235. The partial sequences of rRNA-gene revealed few mutation sites on nucleotide base pairs. However, the mutations detected on rRNA gene of UF16 were less than 1 % of total base pairs and its sequence showed 99 % homology with the wild type strain. These mutations in UF16 could not be linked to phenotypic or genotypic changes on CoQ10 biosynthetic pathway that resulted in improved yield. Hence, investigating the mutations responsible for deregulation of CoQ10 pathway is essential to understand the cause of overproduction in UF16. Phylogenetic analysis based on RAPD bands and rRNA gene sequences coupled with morphological variations, exhibited the novelty of mutant UF16 having potential for improved CoQ10 production.

The production of coenzyme Q10 in microorganisms

Coenzyme Q10 has emerged as a valuable molecule for pharmaceutical and cosmetic applications. Therefore, research into producing and optimizing coenzyme Q10 via microbial fermentation is ongoing. There are two major paths being explored for maximizing production of this molecule to commercially advantageous levels. The first entails using microbes that naturally produce coenzyme Q10 as fermentation biocatalysts and optimizing the fermentation parameters in order to reach industrial levels of production. However, the natural coenzyme Q10-producing microbes tend to be intractable for industrial fermentation settings. The second path to coenzyme Q10 production being explored is to engineer Escherichia coli with the ability to biosynthesize this molecule in order to take advantage of its more favourable fermentation characteristics and the well-understood array of genetic tools available for this bacteria. Although many studies have attempted to over-produce coenzyme Q10 in E. coli through genetic engineering, production titres still remain below those of the natural coenzyme Q10-producing microorganisms. Current research is providing the knowledge needed to alleviate the bottlenecks involved in producing coenzyme Q10 from an E. coli strain platform and the fermentation parameters that could dramatically increase production titres from natural microbial producers. Synthesizing the lessons learned from both approaches may be the key towards a more cost-effective coenzyme Q10 industry.

Recombinant expression of His-tagged saposin B and pH-dependent binding to the lipid coenzyme Q10

The use of coenzyme Q10 (CoQ10) has been increasing rapidly during recent years due to its postulated beneficial properties in human health, providing energy and antioxidant protection. There are no known negative side effects of CoQ10 even at very high levels. Recently, native saposin B (sapB) has been shown to bind CoQ10 and subsequently be excreted. It is thought that this interaction between sapB and CoQ10 could be a mechanism to avoid any possible CoQ10 toxicity. The interaction between sapB and CoQ10 is poorly understood. Here we present an increased fermentative yield of recombinant sapB and demonstrate that recombinant sapB will bind CoQ10 in a pH-dependent manner similar to sapB binding with other lipids. SapB was coated onto an IMAC (immobilized metal affinity chromatography) resin and successfully bound CoQ10 at pH 5.0 with release of the CoQ10 at pH 9.0.