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Mevalonate production from ethanol by direct conversion through acetyl-CoA using recombinant Pseudomonas putida, a novel biocatalyst for terpenoid production.

ABSTRACT: BACKGROUND:Bioethanol is one of the most representative eco-friendly fuels developed to replace the non-renewable fossil fuels and is the most successful commercially available bio-conversion technology till date. With the availability of inexpensive carbon sources, such as cellulosic biomass, bioethanol production has become cheaper and easier to perform, which can facilitate the development of methods for converting ethanol into higher value-added biochemicals. In this study, a bioconversion process using Pseudomonas putida as a biocatalyst was established, wherein ethanol was converted to mevalonate. Since ethanol can be converted directly to acetyl-CoA, bypassing its conversion to pyruvate, there is a possibility that ethanol can be converted to mevalonate without producing pyruvate-derived by-products. Furthermore, P. putida seems to be highly resistant to the toxicity caused by terpenoids, and thus can be useful in conducting terpenoid production research. RESULTS:In this study, we first expressed the core genes responsible for mevalonate production (atoB, mvaS, and mvaE) in P. putida and mevalonate production was confirmed. Thereafter, through an improvement in genetic stability and ethanol metabolism manipulation, mevalonate production was enhanced up to 2.39-fold (1.70 g/L vs. 4.07 g/L) from 200 mM ethanol with an enhancement in reproducibility of mevalonate production. Following this, the metabolic characteristics related to ethanol catabolism and mevalonate production were revealed by manipulations to reduce fatty acid biosynthesis and optimize pH by batch fermentation. Finally, we reached a product yield of 0.41 g mevalonate/g ethanol in flask scale culture and 0.32 g mevalonate/g ethanol in batch fermentation. This is the highest experimental yield obtained from using carbon sources other than carbohydrates till date and it is expected that further improvements will be made through the development of fermentation methods. CONCLUSION:Pseudomonas putida was investigated as a biocatalyst that can efficiently convert ethanol to mevalonate, the major precursor for terpenoid production, and this research is expected to open new avenues for the production of terpenoids using microorganisms that have not yet reached the stage of mass production.

SUBMITTER: Yang J

PROVIDER: S-EPMC6786281 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Mevalonate production from ethanol by direct conversion through acetyl-CoA using recombinant Pseudomonas putida, a novel biocatalyst for terpenoid production.

Yang Jeongmo J Son Ji Hee JH Kim Hyeonsoo H Cho Sukhyeong S Na Jeong-Geol JG Yeon Young Joo YJ Lee Jinwon J Lee Jinwon J

Microbial cell factories 20191010 1

<h4>Background</h4>Bioethanol is one of the most representative eco-friendly fuels developed to replace the non-renewable fossil fuels and is the most successful commercially available bio-conversion technology till date. With the availability of inexpensive carbon sources, such as cellulosic biomass, bioethanol production has become cheaper and easier to perform, which can facilitate the development of methods for converting ethanol into higher value-added biochemicals. In this study, a bioconv ...[more]

PMID: 31601210

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Project description:BACKGROUND:Terpenoids, the largest class of natural products in the plant kingdom, have been widely used in medicine. The precursors of terpenoids, isoprene phosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), were synthesized from a mevalonate (MVA) pathway and a 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway respectively. The acetyl-CoA acetyltransferase (AACT) is the initial enzyme in MVA pathway and is considered presently to be essential for terpenoid backbone biosynthesis. The basic research on cytochemistry of terpenoid metabolic enzymes is important for understanding the mechanisms underlying major metabolic processes. However, compartmentalization of AACT in plants is in controversy. Euphorbia helioscopia L. containing laticifers in the whole plant is a famous ancient folk medicine for tumor treatment, and the terpenoid is an active ingredient. Furthermore, the laticifer cell is the main synthesizing and storing site for terpenoids. RESULTS:The gene of AACT was cloned successfully from E. helioscopia, and named as EhAACT. The EhAACT expression has no significant difference among roots, stems and leaves. However, compared with the roots and stems, the EhAACT expression level is slightly higher in leaves. In addition, EhAACT recombinant protein was expressed by procaryotic expression system and anti-EhAACT antibody was prepared, the molecular weight is about 43 kDa. Western blotting results illustrated that the EhAACT antibodies specifically recognized the endogenous proteins in E. helioscopia laticifers. At last, the subcellular localization of EhAACT in E. helioscopia laticifers was observed by using colloidal gold immune-electron microscopy. EhAACT was found to mainly distribute in the endoplasmic reticulum (ER), vacuoles originated from ER and cytosol aound vacuoles originated from ER. CONCLUSIONS:As a result, we speculated that in E. helioscopia laticifers, EhAACT located in cytosol would be transferred to small vacuoles dilated from ER, and the precursors of terpenoids were synthesized in these small vacuoles, then terpenoids were further synthesized into latex particles. This result would provide theoretical basis for regulating and controlling of terpenoid biosynthesis in laticifers.

Project description:With increasing concern about the environmental impact of a petroleum based economy, focus has shifted towards greener production strategies including metabolic engineering of microbes for the conversion of plant-based feedstocks to second generation biofuels and industrial chemicals. Saccharomyces cerevisiae is an attractive host for this purpose as it has been extensively engineered for production of various fuels and chemicals. Many of the target molecules are derived from the central metabolite and molecular building block, acetyl-CoA. To date, it has been difficult to engineer S. cerevisiae to continuously convert sugars present in biomass-based feedstocks to acetyl-CoA derived products due to intrinsic physiological constraints-in respiring cells, the precursor pyruvate is directed away from the endogenous cytosolic acetyl-CoA biosynthesis pathway towards the mitochondria, and in fermenting cells pyruvate is directed towards the byproduct ethanol. In this study we incorporated an alternative mode of acetyl-CoA biosynthesis mediated by ATP citrate lyase (ACL) that may obviate such constraints.We characterized the activity of several heterologously expressed ACLs in crude cell lysates, and found that ACL from Aspergillus nidulans demonstrated the highest activity. We employed a push/pull strategy to shunt citrate towards ACL by deletion of the mitochondrial NAD(+)-dependent isocitrate dehydrogenase (IDH1) and engineering higher flux through the upper mevalonate pathway. We demonstrated that combining the two modifications increases accumulation of mevalonate pathway intermediates, and that both modifications are required to substantially increase production. Finally, we incorporated a block strategy by replacing the native ERG12 (mevalonate kinase) promoter with the copper-repressible CTR3 promoter to maximize accumulation of the commercially important molecule mevalonate.By combining the push/pull/block strategies, we significantly improved mevalonate production. We anticipate that this strategy can be used to improve the efficiency with which industrial strains of S. cerevisiae convert feedstocks to acetyl-CoA derived fuels and chemicals.

Project description:Purpose: In order to identify genes for steroid 14α-hydroxylase P450lun and its associated redox partner CPRlun in filamentous fungus Cochliobolus lunatus ATCC#12017 Methods: Strand-specific RNA-seq libraries were constructed for two samples, including (I) Mycelia of C. lunatus treated with mock N, N-dimethylformamide (DMF); (II) Mycelia of C. lunatus treated with 170 mg/L 11-deoxycortisol 21-acetate (RSA) dissolved in N,N-dimethylformamide. For preparation of RNA samples, germinated young mycelia of C. lunatus after 22-24 pre-culture in liquid potato dextrose broth medium were harvested and transferred into a new 30 ml potassium phosphate buffer supplement with either 170 mg/L RSA dissolved in DMF, or an equal volume of DMF as mock. Additional two-hours cultivation was performed to induction of the P-450lun gene expression. Total RNA for samples were isolated using TRIzol reagent (Invitrogen, Grand Island, USA), then used for high-throughput RNA sequencing. The two 150-nt strand-specific paired-end RNA-seq libraries were generated commercially at Novogene Biotechnology Co. Ltd (Tianjin, China) by using Illumina’s Hiseq X Ten platform (Illumina, San Diego, USA). The clean reads were used to create a de novo transcriptome assembly using the Trinity pipeline (v2.4.0). The abundance for each of the resulted transcripts was calculated by RSEM (v1.2.0) using the Fragments Per Kilobase per Million (FPKM) method. Results: A total of 7.1 and 7.9 million 150-bp paired-end clean reads were separately generated from the DMF mock and RSA induced samples,and 23957 transcripts with length more than 600nt were assembled from the pooled reads of both samples using Trinity program. The translated sequences of these transcripts were predicted using TransDecoder, and then used as queries to search against the SWISS-PROT and the Pfam databases for functional annotation. Transcripts DN8493 and DN2353 were separately identified as C.lunatus P-450lun and CPRlun genes. Conclusions: The 14β-hydroxylase system of C.lunatus was deciphered by transcriptome analysis.

Dataset Information

Mevalonate production from ethanol by direct conversion through acetyl-CoA using recombinant Pseudomonas putida, a novel biocatalyst for terpenoid production.

Publications

Mevalonate production from ethanol by direct conversion through acetyl-CoA using recombinant Pseudomonas putida, a novel biocatalyst for terpenoid production.

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