Chem Soc Rev View Article Online REVIEW ARTICLE View Journal Synthesis of chemicals by metabolic engineering of microbes Cite this: DOI: 10.1039/c5cs00159e Xinxiao Sun,†a Xiaolin Shen,†a Rachit Jain,†b Yuheng Lin,b Jian Wang,b Jing Sun,a Jia Wang,a Yajun Yan*c and Qipeng Yuan*a Metabolic engineering is a powerful tool for the sustainable production of chemicals. Over the years, the exploration of microbial, animal and plant metabolism has generated a wealth of valuable genetic information. The prudent application of this knowledge on cellular metabolism and biochemistry has enabled the construction of novel metabolic pathways that do not exist in nature or enhance existing ones. The hand in hand development of computational technology, protein science and genetic manipulation tools has formed the basis of powerful emerging technologies that make the production of green Received 19th February 2015 chemicals and fuels a reality. Microbial production of chemicals is more feasible compared to plant and DOI: 10.1039/c5cs00159e animal systems, due to simpler genetic make-up and amenable growth rates. Here, we summarize the recent progress in the synthesis of biofuels, value added chemicals, pharmaceuticals and nutraceuticals via www.rsc.org/csr metabolic engineering of microbes. 1. Introduction and on the other hand has led to severe environmental damage and pollution. Immoderate exploitation and consumption has Since the industrial revolution oil has become the blood of our depleted oil reserves drastically over the past 150 years as the economy, serving as the major source of energy, petrochemicals majority of the fuels and chemicals are currently produced and influencing the market of a plethora of industries globally. using petrochemical feedstocks. Generally, the production of Over-dependence on oil has on one hand led to rapid urbanization, chemicals via chemical approaches has advantages of being a well established production platform associated with low pro- a State Key Laboratory of Chemical Resource Engineering, Beijing University of duction costs. However, some severe drawbacks exist in petroleum- Chemical Technology, 15#, Beisanhuan East Road, Chaoyang District, based manufacturing approaches, such as: (a) the use of toxic/ Published on 05 May 2015. Downloaded by University of Georgia 08/05/2015 03:43:57. Beijing 100029, China. E-mail: [email protected]; Tel: +86-13601162675 environmentally harmful or expensive catalysts, (b) the generation b College of Engineering, University of Georgia, Athens, GA 30602, USA of toxic intermediates, (c) requirements of high temperature– c BioChemical Engineering Program, College of Engineering, University of Georgia, pressure processes, (d) high energy inputs, (e) the production 601B Driftmier Engineering Center, Athens, GA 30602, USA. E-mail: [email protected]; Tel: +1-706-542-8293 of stereo-specific chemicals is difficult. The concerns of oil † Xinxiao Sun, Xiaolin Shen and Rachit Jain contributed equally to this work. crisis and environmental deterioration compel us to look Xinxiao Sun obtained his BS degree Xiaolin Shen obtained her PhD in Pharmaceutical Engineering from degree from Beijing University Beijing University of Chemical of Chemical Technology (2013). Technology (2008). He then joined From 2011 to 2012 she was Prof. Qipeng Yuan’s group and is working as a visiting student now a PhD candidate. Since in Dr Yajun Yan’s group and 2012, he has been working as a her research focus is on bio- visiting student in Dr Yajun Yan’s synthesis of chemicals. From group. His research work mainly 2013, she has been working as focuses on metabolic engineering a lecturer in Beijing University and synthetic biology. of Chemical Technology. She is currently interested in meta- Xinxiao Sun Xiaolin Shen bolic engineering and protein engineering. This journal is © The Royal Society of Chemistry 2015 Chem.Soc.Rev. View Article Online Review Article Chem Soc Rev for alternative ways to produce petroleum-based fuels and in its contiguous fields. DNA sequencing and bioinformatics chemicals. analysis reveal new metabolic pathways and enzyme variants; While the biological production of commodity chemicals has enrichment in protein structure information provides founda- gained significant interest over the years by tapping into the tion for rational protein engineering; advanced analytical tools petrochemical market, the biosynthesis of natural products via identify pathway bottlenecks from RNA, protein or metabolite metabolic engineering has tapped into the large pharmaceutical levels; the availability of a series of genetic tools facilitates and food industry markets. Natural products are a rich source of pathway optimization; advancement in fermentation technology food additives, pharmaceuticals and nutraceuticals, which are enables scale up for industrial scale production.1 widely used in our daily life. The industrial scale production of Microbes (eukaryotic or prokaryotic) that have a simple genetic these compounds by extraction is inefficient and uneconomical background and a fast growth rate are usually used as hosts to due to two reasons: (1) native producers are known to usually grow produce various compounds. This strategy serves both metabolic slowly;(2)theamountoftargetcompoundsgeneratedbynative logic as well as industrial scale process economics. Some success- producers is not in significant quantities. Metabolic engineering ful examples include the production of 1,3-propanediol in of microbes provides a promising alternative for the production of Escherichia coli,2 engineering Saccharomyces cerevisiae for the these petroleum-derived or natural compounds. production of antimalarial drug precursor artemisinic acid.3 Metabolic engineering is a technique that first emerged in the While E. coli and S. cerevisiae are the two most commonly used early 1990s. Since then, this technology has been developing rapidly, hosts for metabolic engineering, other non-conventional hosts which has been greatly dependent on the significant advances have also been explored for their distinctiveness. In this review, Rachit Jain is a Doctoral Yuheng Lin is the Chief Candidate at the University of Technology Officer of BiotecEra Georgia, Athens, GA, USA. He Inc. He received his PhD degree has been working in Dr Yajun in 2014 from the University of Yan’s research group since 2010. Georgia. His research is focused He obtained BE (2009) in on the development of enzymatic Biotechnology from Visvesvaraya and microbial platforms for the Technological University, India. cost-effective production of bio- His current research interests fuels, bulk chemicals and pharma- include the biological manu- ceuticals. The projects involve facture of high value and bulk multiple disciplines including chemicals by metabolic engineer- biochemistry, molecular biology, Rachit Jain ing and protein engineering. Yuheng Lin microbiology, metabolic engineer- ing, and synthetic biology. Published on 05 May 2015. Downloaded by University of Georgia 08/05/2015 03:43:57. Yajun Yan is an Assistant Professor Qipeng Yuan is a professor at of BioChemical Engineering at Beijing University of Chemical the College of Engineering, the Technology. He obtained his PhD University of Georgia. He obtained degree in Chemical Engineering BS (1999) and MS (2002) in from Tianjin University (1997). Biochemical Engineering from He then started postdoctoral Beijing University of Chemical research with Prof. Runyu Ma in Technology, and PhD (2008) the Department of Chemical in Chemical and Biological Engineering, Beijing University of Engineering from the State Chemical Technology (1997–1999). University of New York at His research interests cover many Buffalo. He was a postdoctoral fields in biochemical engineering, Yajun Yan scholar at the University of Qipeng Yuan metabolic engineering, especially California, Los Angeles from biosynthesis of natural products. 2008–2010. His research focuses on developing enzymatic and microbial approaches for the production of pharmaceutically important compounds, fuels and renewable chemicals. He founded BiotecEra Inc. in 2014, to commercialize technologies related to the microbial production of value-added chemicals. Chem.Soc.Rev. This journal is © The Royal Society of Chemistry 2015 View Article Online Chem Soc Rev Review Article Table 1 Synthesis of chemicals by metabolic engineering of microbes. This table represents the most significant metabolic engineering efforts and may not necessarily represent the highest titers achieved biologically Category Subcategory Chemical Applications Host/carbon source Titer (g LÀ1) Ref. Biofuels Alcohols Ethanol Fuel additive, plastics, solvents, S. cerevisiae/DEHU 36.2 15 p-xylene, isobutyl acetate, isobutyl and mannitol 1-Propanol esters E. coli/glucose 10.8 23 Isopropanol E. coli/glucose 143 26 1-Butnaol E. coli/glucose 30 35 Isobutanol E. coli/glucose 50 37 Fatty acids Fuel additive, detergents, paints, food E. coli/glucose 6.9 60 products, cosmetics, etc. Alkanes/alkenes Natural gas, gasoline, diesel, aviation E. coli/glucose 0.58 66 kerosene Other Hydrogen Fuel E. coli/glycerol 1 mol molÀ1 69 Bulk chemicals Diols 2,3-Butanediol Polymers, antifreeze, perfumes, Serratia 152 81 printing ink, food supplements, marcescens/sucrose 1,4-Butanediol pharmaceuticals, fumigants, sol- E. coli/glucose 18 84 1,3-Propanediol vents, cosmetics, detergents E. coli/glucose 135 2 1,2-Propanediol E. coli/glucose 5.1 21 Organic acids Lactic acid Pharmaceuticals, polymer pre- E. coli/glucose 142.2 115