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Cordova LT, Palmer CM, Alper HS. Shifting the distribution: modulation of the lipid profile in Yarrowia lipolytica via iron content. Appl Microbiol Biotechnol 2022; 106:1571-1581. [PMID: 35099573 DOI: 10.1007/s00253-022-11800-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 01/14/2022] [Accepted: 01/21/2022] [Indexed: 11/02/2022]
Abstract
Microbial fermentation offers a sustainable source of fuels, commodity chemicals, and pharmaceuticals, yet strain performance is influenced greatly by the growth media selected. Specifically, trace metals (e.g., iron, copper, manganese, zinc, and others) are critical for proper growth and enzymatic function within microorganisms yet are non-standardized across media formulation. In this work, the effect of trace metal supplementation on the lipid production profile of Yarrowia lipolytica was explored using tube scale fermentation followed by biomass and lipid characterization. Addition of iron (II) to the chemically defined Yeast Synthetic Complete (YSC) medium increased final optical density nearly twofold and lipid production threefold, while addition of copper (II) had no impact. Additionally, dose-responsive changes in lipid distribution were observed, with the percent of oleic acid increasing and stearic acid decreasing as initial iron concentration increased. These changes were reversible with subsequent iron-selective chelation. Use of rich Yeast Peptone Dextrose (YPD) medium enabled further increases in the production of two specialty oleochemicals ultimately reaching 63 and 47% of the lipid pool as α-linolenic acid and cyclopropane fatty acid, respectively, compared to YSC medium. Selective removal of iron (II) natively present in YPD medium decreased this oleochemical production, ultimately aligning the lipid profile with that of non-supplemented YSC medium. These results provide further insight into the proposed mechanisms for iron regulation in yeasts especially as these productions strains contain a mutant allele of the iron regulator, mga2. The work presented here also suggests a non-genetic method for control of the lipid profile in Y. lipolytica for use in diverse applications. KEY POINTS: • Iron supplementation increases cell density and lipid titer in Yarrowia lipolytica. • Iron addition reversibly alters lipid portfolio increasing linolenic acid. • Removal of iron from YPD media provides a link to enhanced oleochemical production.
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d’Oelsnitz S, Nguyen V, Alper HS, Ellington AD. Evolving a Generalist Biosensor for Bicyclic Monoterpenes. ACS Synth Biol 2022; 11:265-272. [PMID: 34985281 DOI: 10.1021/acssynbio.1c00402] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Prokaryotic transcription factors can be repurposed as analytical and synthetic tools for precise chemical measurement and regulation. Monoterpenes encompass a broad chemical family that are commercially valuable as flavors, cosmetics, and fragrances, but have proven difficult to measure, especially in cells. Herein, we develop genetically encoded, generalist monoterpene biosensors by using directed evolution to expand the effector specificity of the camphor-responsive TetR-family regulator CamR from Pseudomonas putida. Using a novel negative selection coupled with a high-throughput positive screen (Seamless Enrichment of Ligand-Inducible Sensors, SELIS), we evolve CamR biosensors that can recognize four distinct monoterpenes: borneol, fenchol, eucalyptol, and camphene. Different evolutionary trajectories surprisingly yielded common mutations, emphasizing the utility of CamR as a platform for creating generalist biosensors. Systematic promoter optimization driving the reporter increased the system's signal-to-noise ratio to 150-fold. These sensors can serve as a starting point for the high-throughput screening and dynamic regulation of bicyclic monoterpene production strains.
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Biggs BW, Alper HS, Pfleger BF, Tyo KEJ, Santos CNS, Ajikumar PK, Stephanopoulos G. Enabling commercial success of industrial biotechnology. Science 2021; 374:1563-1565. [PMID: 34941395 DOI: 10.1126/science.abj5040] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
[Figure: see text].
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Lad BC, Coleman SM, Alper HS. Microbial valorization of underutilized and nonconventional waste streams. J Ind Microbiol Biotechnol 2021; 49:6371101. [PMID: 34529075 PMCID: PMC9118980 DOI: 10.1093/jimb/kuab056] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 09/14/2021] [Indexed: 12/12/2022]
Abstract
The growing burden of waste disposal coupled with natural resource scarcity has renewed interest in the remediation, valorization, and/or repurposing of waste. Traditional approaches such as composting, anaerobic digestion, use in fertilizers or animal feed, or incineration for energy production extract very little value out of these waste streams. In contrast, waste valorization into fuels and other biochemicals via microbial fermentation is an area of growing interest. In this review, we discuss microbial valorization of nonconventional, aqueous waste streams such as food processing effluents, wastewater streams, and other industrial wastes. We categorize these waste streams as carbohydrate-rich food wastes, lipid-rich wastes, and other industrial wastes. Recent advances in microbial valorization of these nonconventional waste streams are highlighted, along with a discussion of the specific challenges and opportunities associated with impurities, nitrogen content, toxicity, and low productivity.
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Bowman EK, Wagner JM, Yuan SF, Deaner M, Palmer CM, D'Oelsnitz S, Cordova L, Li X, Craig FF, Alper HS. Sorting for secreted molecule production using a biosensor-in-microdroplet approach. Proc Natl Acad Sci U S A 2021; 118:e2106818118. [PMID: 34475218 PMCID: PMC8433520 DOI: 10.1073/pnas.2106818118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 07/28/2021] [Indexed: 11/18/2022] Open
Abstract
Sorting large libraries of cells for improved small molecule secretion is throughput limited. Here, we combine producer/secretor cell libraries with whole-cell biosensors using a microfluidic-based screening workflow. This approach enables a mix-and-match capability using off-the-shelf biosensors through either coencapsulation or pico-injection. We demonstrate the cell type and library agnostic nature of this workflow by utilizing single-guide RNA, transposon, and ethyl-methyl sulfonate mutagenesis libraries across three distinct microbes (Escherichia coli, Saccharomyces cerevisiae, and Yarrowia lipolytica), biosensors from two organisms (E. coli and S. cerevisiae), and three products (triacetic acid lactone, naringenin, and L-DOPA) to identify targets improving production/secretion.
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Wagner JM, Palmer CM, Venkataraman MV, Lauffer LH, Wiggers JM, Williams EV, Yi X, Alper HS. Genome Engineering of Yarrowia lipolytica with the PiggyBac Transposon System. Methods Mol Biol 2021; 2307:1-24. [PMID: 33847979 DOI: 10.1007/978-1-0716-1414-3_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A mutant excision+/integration- piggyBac transposase can be used to seamlessly excise a chromosomally integrated, piggyBac-compatible selection marker cassette from the Yarrowia lipolytica genome. This piggyBac transposase-based genome engineering process allows for both positive selection of targeted homologous recombination events and scarless or footprint-free genome modifications after precise marker recovery. Residual non-native sequences left in the genome after marker excision can be minimized (0-4 nucleotides) or customized (user-defined except for a TTAA tetranucleotide). Both of these options reduce the risk of unintended homologous recombination events in strains with multiple genomic edits. A suite of dual positive/negative selection marker pairs flanked by piggyBac inverted terminal repeats (ITRs) have been constructed and are available for precise genome engineering in Y. lipolytica using this method. This protocol specifically describes the split marker homologous recombination-based disruption of Y. lipolytica ADE2 with a piggyBac ITR-flanked URA3 cassette, followed by piggyBac transposase-mediated excision of the URA3 marker to leave a 50 nucleotide synthetic barcode at the ADE2 locus. The resulting ade2 strain is auxotrophic for adenine, which enables the use of ADE2 as a selectable marker for further strain engineering.
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Yuan SF, Brooks SM, Nguyen AW, Lin WL, Johnston TG, Maynard JA, Nelson A, Alper HS. Bioproduced Proteins On Demand (Bio-POD) in hydrogels using Pichia pastoris. Bioact Mater 2021; 6:2390-2399. [PMID: 33553823 PMCID: PMC7846901 DOI: 10.1016/j.bioactmat.2021.01.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/23/2020] [Accepted: 01/14/2021] [Indexed: 12/20/2022] Open
Abstract
Traditional production of industrial and therapeutic proteins by eukaryotic cells typically requires large-scale fermentation capacity. As a result, these systems are not easily portable or reusable for on-demand protein production applications. In this study, we employ Bioproduced Proteins On Demand (Bio-POD), a F127-bisurethane methacrylate hydrogel-based technique that immobilizes engineered Pichia pastoris for preservable, on-demand production and secretion of medium- and high-molecular weight proteins (in this case, SEAP, α-amylase, and anti-HER2). The gel samples containing encapsulated-yeast demonstrated sustained protein production and exhibited productivity immediately after lyophilization and rehydration. The hydrogel platform described here is the first hydrogel immobilization using a P. pastoris system to produce recombinant proteins of this breadth. These results highlight the potential of this formulation to establish a cost-effective bioprocessing strategy for on-demand protein production.
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Amador-Castro F, García-Cayuela T, Alper HS, Rodriguez-Martinez V, Carrillo-Nieves D. Valorization of pelagic sargassum biomass into sustainable applications: Current trends and challenges. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 283:112013. [PMID: 33508553 DOI: 10.1016/j.jenvman.2021.112013] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/15/2021] [Accepted: 01/16/2021] [Indexed: 06/12/2023]
Abstract
Since long ago, pelagic Sargassum mats have been known to be abundant in the Sargasso Sea, where they provide habitat to diverse organisms. However, over the last few years, massive amounts of pelagic Sargassum have reached the coast of several countries in the Caribbean and West Africa, causing economic and environmental problems. Aiming for lessening the impacts of the blooms, governments and private companies remove the seaweeds from the shore, but this process results expensive. The valorization of this abundant biomass can render Sargassum tides into an economic opportunity and concurrently solve their associated environmental problems. Despite the diverse fields where algae have found applications and the relevance of this recurrent situation, Sargassum biomass remains without large scale applications. Therefore, this review aims to present the potential uses of these algae, identifying the limitations that must be assessed to effectively valorize this bioresource. Due to the constraints identified for each of the presented applications, it is concluded that a biorefinery approach should be developed to effectively valorize this abundant biomass. However, there is an urgent need for investigations focusing on holopelagic Sargassum to be able to truly valorize this seaweed.
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Brooks SM, Alper HS. Applications, challenges, and needs for employing synthetic biology beyond the lab. Nat Commun 2021; 12:1390. [PMID: 33654085 PMCID: PMC7925609 DOI: 10.1038/s41467-021-21740-0] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 02/10/2021] [Indexed: 02/07/2023] Open
Abstract
Synthetic biology holds great promise for addressing global needs. However, most current developments are not immediately translatable to 'outside-the-lab' scenarios that differ from controlled laboratory settings. Challenges include enabling long-term storage stability as well as operating in resource-limited and off-the-grid scenarios using autonomous function. Here we analyze recent advances in developing synthetic biological platforms for outside-the-lab scenarios with a focus on three major application spaces: bioproduction, biosensing, and closed-loop therapeutic and probiotic delivery. Across the Perspective, we highlight recent advances, areas for further development, possibilities for future applications, and the needs for innovation at the interface of other disciplines.
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Sun L, Xin F, Alper HS. Bio-synthesis of food additives and colorants-a growing trend in future food. Biotechnol Adv 2021; 47:107694. [PMID: 33388370 DOI: 10.1016/j.biotechadv.2020.107694] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 12/24/2020] [Accepted: 12/27/2020] [Indexed: 02/07/2023]
Abstract
Food additives and colorants are extensively used in the food industry to improve food quality and safety during processing, storage and packing. Sourcing of these molecules is predominately through three means: extraction from natural sources, chemical synthesis, and bio-production, with the first two being the most utilized. However, growing demands for sustainability, safety and "natural" products have renewed interest in using bio-based production methods. Likewise, the move to more cultured foods and meat alternatives requires the production of new additives and colorants. The production of bio-based food additives and colorants is an interdisciplinary research endeavor and represents a growing trend in future food. To highlight the potential of microbial hosts for food additive and colorant production, we focus on current advances for example molecules based on their utilization stage and bio-production yield as follows: (I) approved and industrially produced with high titers; (II) approved and produced with decent titers (in the g/L range), but requiring further engineering to reduce production costs; (III) approved and produced with very early stage titers (in the mg/L range); and (IV) new/potential candidates that have not been approved but can be sourced through microbes. Promising approaches, as well as current challenges and future directions will also be thoroughly discussed for the bioproduction of these food additives and colorants.
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Gordillo Sierra AR, Alper HS. Progress in the metabolic engineering of bio-based lactams and their ω-amino acids precursors. Biotechnol Adv 2020; 43:107587. [DOI: 10.1016/j.biotechadv.2020.107587] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/29/2020] [Accepted: 07/07/2020] [Indexed: 01/08/2023]
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Tang RQ, Wagner JM, Alper HS, Zhao XQ, Bai FW. Design, Evolution, and Characterization of a Xylose Biosensor in Escherichia coli Using the XylR/ xylO System with an Expanded Operating Range. ACS Synth Biol 2020; 9:2714-2722. [PMID: 32886884 DOI: 10.1021/acssynbio.0c00225] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Genetically encoded biosensors are extensively utilized in synthetic biology and metabolic engineering. However, reported xylose biosensors are far too sensitive with a limited operating range to be useful for most sensing applications. In this study, we describe directed evolution of Escherichia coli XylR, and construction of biosensors based on XylR and the corresponding operator xylO. The operating range of biosensors containing the mutant XylR was increased by nearly 10-fold comparing with the control. Two individual amino acid mutations (either L73P or N220T) in XylR were sufficient to extend the linear response range to upward of 10 g/L xylose. The evolved biosensors described here are well suited for developing whole-cell biosensors for detecting varying xylose concentrations across an expanded range. As an alternative use of this system, we also demonstrate the utility of XylR and xylO as a xylose inducible system to enable graded gene expression through testing with β-galactosidase gene and the lycopene synthetic pathway. This evolution strategy identified a less-sensitive biosensor for real applications, thus providing new insights into strategies for expanding operating ranges of other biosensors for synthetic biology applications.
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Cordova LT, Lad BC, Ali SA, Schmidt AJ, Billing JM, Pomraning K, Hofstad B, Swita MS, Collett JR, Alper HS. Valorizing a hydrothermal liquefaction aqueous phase through co-production of chemicals and lipids using the oleaginous yeast Yarrowia lipolytica. BIORESOURCE TECHNOLOGY 2020; 313:123639. [PMID: 32534224 DOI: 10.1016/j.biortech.2020.123639] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/02/2020] [Accepted: 06/03/2020] [Indexed: 06/11/2023]
Abstract
Hydrothermal liquefaction is a promising technology to upgrade wet organic waste into a biocrude oil for diesel or jet fuel; however, this process generates an acid-rich aqueous phase which poses disposal issues. This hydrothermal liquefaction aqueous phase (HTL-AP) contains organic acids, phenol, and other toxins. This work demonstrates that Y. lipolytica as a unique host to valorize HTL-AP into a variety of co-products. Specifically, strains of Y. lipolytica can tolerate HTL-AP at 10% in defined media and 25% in rich media. The addition of HTL-AP enhances production of the polymer precursor itaconic acid by 3-fold and the polyketide triacetic acid lactone at least 2-fold. Additional co-products (lipids and citric acid) were produced in these fermentations. Finally, bioreactor cultivation enabled 21.6 g/L triacetic acid lactone from 20% HTL-AP in mixed sugar hydrolysate. These results demonstrate the first use of Y. lipolytica in HTL-AP valorization toward production of a portfolio of value-added compounds.
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Bowman EK, Deaner M, Cheng JF, Evans R, Oberortner E, Yoshikuni Y, Alper HS. Bidirectional titration of yeast gene expression using a pooled CRISPR guide RNA approach. Proc Natl Acad Sci U S A 2020; 117:18424-18430. [PMID: 32690674 PMCID: PMC7414176 DOI: 10.1073/pnas.2007413117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Most classic genetic approaches utilize binary modifications that preclude the identification of key knockdowns for essential genes or other targets that only require moderate modulation. As a complementary approach to these classic genetic methods, we describe a plasmid-based library methodology that affords bidirectional, graded modulation of gene expression enabled by tiling the promoter regions of all 969 genes that comprise the ito977 model of Saccharomyces cerevisiae's metabolic network. When coupled with a CRISPR-dCas9-based modulation and next-generation sequencing, this method affords a library-based, bidirection titration of gene expression across all major metabolic genes. We utilized this approach in two case studies: growth enrichment on alternative sugars, glycerol and galactose, and chemical overproduction of betaxanthins, leading to the identification of unique gene targets. In particular, we identify essential genes and other targets that were missed by classic genetic approaches.
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Yuan SF, Yi X, Johnston TG, Alper HS. De novo resveratrol production through modular engineering of an Escherichia coli-Saccharomyces cerevisiae co-culture. Microb Cell Fact 2020; 19:143. [PMID: 32664999 PMCID: PMC7362445 DOI: 10.1186/s12934-020-01401-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/07/2020] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Resveratrol is a plant secondary metabolite with diverse, potential health-promoting benefits. Due to its nutraceutical merit, bioproduction of resveratrol via microbial engineering has gained increasing attention and provides an alternative to unsustainable chemical synthesis and straight extraction from plants. However, many studies on microbial resveratrol production were implemented with the addition of water-insoluble phenylalanine or tyrosine-based precursors to the medium, limiting in the sustainable development of bioproduction. RESULTS Here we present a novel coculture platform where two distinct metabolic background species were modularly engineered for the combined total and de novo biosynthesis of resveratrol. In this scenario, the upstream Escherichia coli module is capable of excreting p-coumaric acid into the surrounding culture media through constitutive overexpression of codon-optimized tyrosine ammonia lyase from Trichosporon cutaneum (TAL), feedback-inhibition-resistant 3-deoxy-d-arabinoheptulosonate-7-phosphate synthase (aroGfbr) and chorismate mutase/prephenate dehydrogenase (tyrAfbr) in a transcriptional regulator tyrR knockout strain. Next, to enhance the precursor malonyl-CoA supply, an inactivation-resistant version of acetyl-CoA carboxylase (ACC1S659A,S1157A) was introduced into the downstream Saccharomyces cerevisiae module constitutively expressing codon-optimized 4-coumarate-CoA ligase from Arabidopsis thaliana (4CL) and resveratrol synthase from Vitis vinifera (STS), and thus further improve the conversion of p-coumaric acid-to-resveratrol. Upon optimization of the initial inoculation ratio of two populations, fermentation temperature, and culture time, this co-culture system yielded 28.5 mg/L resveratrol from glucose in flasks. In further optimization by increasing initial net cells density at a test tube scale, a final resveratrol titer of 36 mg/L was achieved. CONCLUSIONS This is first study that demonstrates the use of a synthetic E. coli-S. cerevisiae consortium for de novo resveratrol biosynthesis, which highlights its potential for production of other p-coumaric-acid or resveratrol derived biochemicals.
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Bowman EK, Alper HS. Microdroplet-Assisted Screening of Biomolecule Production for Metabolic Engineering Applications. Trends Biotechnol 2020; 38:701-714. [DOI: 10.1016/j.tibtech.2019.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/30/2019] [Accepted: 11/07/2019] [Indexed: 12/19/2022]
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Sun L, Alper HS. Non-conventional hosts for the production of fuels and chemicals. Curr Opin Chem Biol 2020; 59:15-22. [PMID: 32348879 DOI: 10.1016/j.cbpa.2020.03.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 03/18/2020] [Accepted: 03/25/2020] [Indexed: 12/16/2022]
Abstract
Biotechnology offers a green alternative for the production of fuels and chemicals using microbes. Although traditional model hosts such as Escherichia coli and Saccharomyces cerevisiae have been widely studied and used, they may not be the best hosts for industrial application. In this review, we explore recent advances in the use of nonconventional hosts for the production of a variety of fuel, cosmetics, perfumes, food, and pharmaceuticals. Specifically, we highlight twenty-seven popular molecules with a special focus on recent progress and metabolic engineering strategies to enable improved production of fuels and chemicals. These examples demonstrate the promise of nonconventional host engineering.
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Yuan SF, Alper HS. Improving Spinach2-and Broccoli-based biosensors for single and double analytes. ACTA ACUST UNITED AC 2020. [DOI: 10.1016/j.biotno.2020.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Tang R, Ye P, Alper HS, Liu Z, Zhao X, Bai F. Identification and characterization of novel xylose isomerases from a Bos taurus fecal metagenome. Appl Microbiol Biotechnol 2019; 103:9465-9477. [PMID: 31701197 DOI: 10.1007/s00253-019-10161-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 09/08/2019] [Accepted: 09/28/2019] [Indexed: 12/31/2022]
Abstract
Discovering sugar metabolism genes is of great interest for lignocellulosic biorefinery. Xylose isomerases (XIs) were commonly screened from metagenomes derived from bovine rumen, soil, and other sources. However, so far, XIs and other sugar-utilizing enzymes have not been discovered from fecal metagenomes. In this study, environmental DNA from the fecal samples collected from yellow cattle (Bos taurus) was sequenced and analyzed. In the whole 14.26 Gbp clean data, 92 putative XIs were annotated. After sequence analysis, seven putative XIs were heterologously expressed in Escherichia coli and characterized in vitro. The XIs 58444 and 58960 purified from E. coli exhibited 22% higher enzyme activity when compared with that of the native E. coli XI. The XI 58444, similar to the XI from Lachnospira multipara, exhibited a relatively stable activity profile across different pH conditions. Four XIs were further investigated in budding yeast Saccharomyces cerevisiae after codon optimization. Overexpression of the codon-optimized 58444 enabled S. cerevisiae to utilize 6.4 g/L xylose after 96 h without any other genetic manipulations, which is 56% higher than the control yeast strain overexpressing an optimized XI gene xylA*3 selected by three rounds of mutation. Our results provide evidence that a bovine fecal metagenome is a novel and valuable source of XIs and other industrial enzymes for biotechnology applications.
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Deaner M, Alper HS. Enhanced scale and scope of genome engineering and regulation using CRISPR/Cas in Saccharomyces cerevisiae. FEMS Yeast Res 2019; 19:foz076. [PMID: 31665284 DOI: 10.1093/femsyr/foz076] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 10/24/2019] [Indexed: 12/13/2022] Open
Abstract
Although only 6 years old, the CRISPR system has blossomed into a tool for rapid, on-demand genome engineering and gene regulation in Saccharomyces cerevisiae. In this minireview, we discuss fundamental CRISPR technologies, tools to improve the efficiency and capabilities of gene targeting, and cutting-edge techniques to explore gene editing and transcriptional regulation at genome scale using pooled approaches. The focus is on applications to metabolic engineering with topics including development of techniques to edit the genome in multiplex, tools to enable large numbers of genetic modifications using pooled single-guide RNA libraries and efforts to enable programmable transcriptional regulation using endonuclease-null Cas enzymes.
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Cordova LT, Butler J, Alper HS. Direct production of fatty alcohols from glucose using engineered strains of Yarrowia lipolytica. Metab Eng Commun 2019; 10:e00105. [PMID: 32547923 PMCID: PMC7283507 DOI: 10.1016/j.mec.2019.e00105] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/11/2019] [Accepted: 10/26/2019] [Indexed: 11/22/2022] Open
Abstract
Fatty alcohols are important industrial oleochemicals with broad applications and a growing market. Here, we sought to engineer Yarrowia lipolytica to serve as a renewable source of fatty alcohols (specifically hexadecanol, heptadecanol, octadecanol, and oleyl alcohol) directly from glucose. Through screening four fatty acyl-CoA reductase (FAR) enzyme variants across two engineered background strains, we identified that MhFAR enabled the highest production. Further strain engineering, fed-batch flask cultivation, and extractive fermentation improved the fatty alcohol titer to 1.5 g/L. Scale-up of this strain in a 2L bioreactor led to 5.8 g/L total fatty alcohols at an average yield of 36 mg/g glucose with a maximum productivity of 39 mg/L hr. Finally, we utilized this fatty alcohol reductase to generate a customized fatty alcohol, linolenyl alcohol, from α-linolenic acid. Overall, this work demonstrates Y. lipolytica is a robust chassis for diverse fatty alcohol production and highlights the capacity to obtain high titers and yields from a purely minimal media formulation directly from glucose without the need for complex additives. Survey of FAR function was assessed in two background strains. Direct production of fatty alcohols from glucose was enabled in minimal media. Fatty alcohol was produced at titers of 5.8 g/L in bioreactors with 36 mg/g average yield. Production of a customized fatty alcohol, linolenyl alcohol, was demonstrated.
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Li H, Alper HS. Producing Biochemicals in
Yarrowia lipolytica
from Xylose through a Strain Mating Approach. Biotechnol J 2019; 15:e1900304. [DOI: 10.1002/biot.201900304] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/16/2019] [Indexed: 11/06/2022]
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48
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Alper HS, Wittmann C. Systems Metabolic Engineering Approaches for Rewiring Cells. Biotechnol J 2019; 14:e1900312. [PMID: 31476113 DOI: 10.1002/biot.201900312] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Indexed: 11/09/2022]
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49
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Cheng JK, Morse NJ, Wagner JM, Tucker SK, Alper HS. Design and Evaluation of Synthetic Terminators for Regulating Mammalian Cell Transgene Expression. ACS Synth Biol 2019; 8:1263-1275. [PMID: 31091408 DOI: 10.1021/acssynbio.8b00285] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Tuning heterologous gene expression in mammalian production hosts has predominantly relied upon engineering the promoter elements driving the transcription of the transgene. Moreover, most regulatory elements have borrowed genetic sequences from viral elements. Here, we generate a set of 10 rational and 30 synthetic terminators derived from nonviral elements and evaluate them in the HT1080 and HEK293 cell lines to demonstrate that they are comparable in terms of tuning gene expression/protein output to the viral SV40 element and often require less sequence footprint. The mode of action of these terminators is determined to be an increase in mRNA half-life. Furthermore, we demonstrate that constructs comprising completely nonviral regulatory elements ( i.e., promoters and terminators) can outperform commonly used, strong viral based elements by nearly 2-fold. Ultimately, this novel set of terminators expanded our genetic toolkit for engineering mammalian host cells.
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50
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Schwartz C, Cheng JF, Evans R, Schwartz CA, Wagner JM, Anglin S, Beitz A, Pan W, Lonardi S, Blenner M, Alper HS, Yoshikuni Y, Wheeldon I. Validating genome-wide CRISPR-Cas9 function improves screening in the oleaginous yeast Yarrowia lipolytica. Metab Eng 2019; 55:102-110. [PMID: 31216436 DOI: 10.1016/j.ymben.2019.06.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 06/06/2019] [Accepted: 06/14/2019] [Indexed: 12/26/2022]
Abstract
Genome-wide mutational screens are central to understanding the genetic underpinnings of evolved and engineered phenotypes. The widespread adoption of CRISPR-Cas9 genome editing has enabled such screens in many organisms, but identifying functional sgRNAs still remains a challenge. Here, we developed a methodology to quantify the cutting efficiency of each sgRNA in a genome-scale library, and in doing so improve screens in the biotechnologically important yeast Yarrowia lipolytica. Screening in the presence and absence of native DNA repair enabled high-throughput quantification of sgRNA function leading to the identification of high efficiency sgRNAs that cover 94% of genes. Library validation enhanced the classification of essential genes by identifying inactive guides that create false negatives and mask the effects of successful disruptions. Quantification of guide effectiveness also creates a dataset from which determinants of CRISPR-Cas9 can be identified. Finally, application of the library identified novel mutations for metabolic engineering of high lipid accumulation.
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