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Gronchi N, De Bernardini N, Cripwell RA, Treu L, Campanaro S, Basaglia M, Foulquié-Moreno MR, Thevelein JM, Van Zyl WH, Favaro L, Casella S. Natural Saccharomyces cerevisiae Strain Reveals Peculiar Genomic Traits for Starch-to-Bioethanol Production: the Design of an Amylolytic Consolidated Bioprocessing Yeast. Front Microbiol 2022; 12:768562. [PMID: 35126325 PMCID: PMC8815085 DOI: 10.3389/fmicb.2021.768562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 12/17/2021] [Indexed: 11/13/2022] Open
Abstract
Natural yeast with superior fermentative traits can serve as a platform for the development of recombinant strains that can be used to improve the sustainability of bioethanol production from starch. This process will benefit from a consolidated bioprocessing (CBP) approach where an engineered strain producing amylases directly converts starch into ethanol. The yeast Saccharomyces cerevisiae L20, previously selected as outperforming the benchmark yeast Ethanol Red, was here subjected to a comparative genomic investigation using a dataset of industrial S. cerevisiae strains. Along with Ethanol Red, strain L20 was then engineered for the expression of α-amylase amyA and glucoamylase glaA genes from Aspergillus tubingensis by employing two different approaches (delta integration and CRISPR/Cas9). A correlation between the number of integrated copies and the hydrolytic abilities of the recombinants was investigated. L20 demonstrated important traits for the construction of a proficient CBP yeast. Despite showing a close relatedness to commercial wine yeast and the benchmark Ethanol Red, a unique profile of gene copy number variations (CNVs) was found in L20, mainly encoding membrane transporters and secretion pathway proteins but also the fermentative metabolism. Moreover, the genome annotation disclosed seven open reading frames (ORFs) in L20 that are absent in the reference S288C genome. Genome engineering was successfully implemented for amylase production. However, with equal amylase gene copies, L20 proved its proficiency as a good enzyme secretor by exhibiting a markedly higher amylolytic activity than Ethanol Red, in compliance to the findings of the genomic exploration. The recombinant L20 dT8 exhibited the highest amylolytic activity and produced more than 4 g/L of ethanol from 2% starch in a CBP setting without the addition of supplementary enzymes. Based on the performance of this strain, an amylase/glucoamylase ratio of 1:2.5 was suggested as baseline for further improvement of the CBP ability. Overall, L20 showed important traits for the future construction of a proficient CBP yeast. As such, this work shows that natural S. cerevisiae strains can be used for the expression of foreign secreted enzymes, paving the way to strain improvement for the starch-to-bioethanol route.
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Affiliation(s)
- Nicoletta Gronchi
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padua, Legnaro, Italy
| | | | - Rosemary A Cripwell
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | - Laura Treu
- Department of Biology, University of Padua, Padua, Italy
| | | | - Marina Basaglia
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padua, Legnaro, Italy
| | | | - Johan M Thevelein
- Department of Molecular Microbiology, VIB, KU Leuven, Leuven, Belgium
- NovelYeast Bv, Open Bio-Incubator, Erasmus High School, Jette, Belgium
| | - Willem H Van Zyl
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | - Lorenzo Favaro
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padua, Legnaro, Italy
| | - Sergio Casella
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padua, Legnaro, Italy
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Favaro L, Viktor MJ, Rose SH, Viljoen-Bloom M, van Zyl WH, Basaglia M, Cagnin L, Casella S. Consolidated bioprocessing of starchy substrates into ethanol by industrial Saccharomyces cerevisiae strains secreting fungal amylases. Biotechnol Bioeng 2015; 112:1751-60. [PMID: 25786804 DOI: 10.1002/bit.25591] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/03/2015] [Accepted: 03/09/2015] [Indexed: 01/16/2023]
Abstract
The development of a yeast strain that converts raw starch to ethanol in one step (called Consolidated Bioprocessing, CBP) could significantly reduce the commercial costs of starch-based bioethanol. An efficient amylolytic Saccharomyces cerevisiae strain suitable for industrial bioethanol production was developed in this study. Codon-optimized variants of the Thermomyces lanuginosus glucoamylase (TLG1) and Saccharomycopsis fibuligera α-amylase (SFA1) genes were δ-integrated into two S. cerevisiae yeast with promising industrial traits, i.e., strains M2n and MEL2. The recombinant M2n[TLG1-SFA1] and MEL2[TLG1-SFA1] yeast displayed high enzyme activities on soluble and raw starch (up to 8118 and 4461 nkat/g dry cell weight, respectively) and produced about 64 g/L ethanol from 200 g/L raw corn starch in a bioreactor, corresponding to 55% of the theoretical maximum ethanol yield (g of ethanol/g of available glucose equivalent). Their starch-to-ethanol conversion efficiencies were even higher on natural sorghum and triticale substrates (62 and 73% of the theoretical yield, respectively). This is the first report of direct ethanol production from natural starchy substrates (without any pre-treatment or commercial enzyme addition) using industrial yeast strains co-secreting both a glucoamylase and α-amylase.
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Affiliation(s)
- Lorenzo Favaro
- Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), Università di Padova, Agripolis, Viale dell'Università 16, 35020, Legnaro (PD), Italy
| | - Marko J Viktor
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | - Shaunita H Rose
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | | | - Willem H van Zyl
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | - Marina Basaglia
- Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), Università di Padova, Agripolis, Viale dell'Università 16, 35020, Legnaro (PD), Italy.
| | - Lorenzo Cagnin
- Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), Università di Padova, Agripolis, Viale dell'Università 16, 35020, Legnaro (PD), Italy
| | - Sergio Casella
- Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), Università di Padova, Agripolis, Viale dell'Università 16, 35020, Legnaro (PD), Italy
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Lee JY, Im YK, Ko HM, Chin JE, Kim IC, Lee HB, Bai S. Direct utilization of purple sweet potato by sake yeasts to produce an anthocyanin-rich alcoholic beverage. Biotechnol Lett 2015; 37:1439-45. [DOI: 10.1007/s10529-015-1811-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 03/02/2015] [Indexed: 10/23/2022]
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Park JY, Lee JY, Choi SH, Ko HM, Kim IC, Lee HB, Bai S. Construction of dextrin and isomaltose-assimilating brewer's yeasts for production of low-carbohydrate beer. Biotechnol Lett 2014; 36:1693-9. [PMID: 24737083 DOI: 10.1007/s10529-014-1530-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/01/2014] [Indexed: 11/27/2022]
Abstract
Most Saccharomyces spp. cannot degrade or ferment dextrin, which is the second most abundant carbohydrate in wort for commercial beer production. Dextrin-degrading brewer's bottom and top yeasts expressing the glucoamylase gene (GAM1) from Debaryomyces occidentalis were developed to produce low-carbohydrate (calorie) beers. GAM1 was constitutively expressed in brewer's yeasts using a rDNA-integration system that contained yeast CUP1 gene coding for copper resistance as a selective marker. The recombinants secreted active glucoamylase, displaying both α-1,4- and α-1,6-debranching activities, that degraded dextrin and isomaltose and consequently grew using them as sole carbon source. One of the recombinant strains expressing GAM1 hydrolyzed 96 % of 2 % (w/v) dextrin and 98 % of 2 % (w/v) isomaltose within 5 days of growth. Growth, substrate assimilation, and enzyme activity of these strains were characterized.
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Affiliation(s)
- Jin-Yeong Park
- Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, 500-757, South Korea
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Blanco CA, Caballero I, Barrios R, Rojas A. Innovations in the brewing industry: light beer. Int J Food Sci Nutr 2014; 65:655-60. [PMID: 24601667 DOI: 10.3109/09637486.2014.893285] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The demand for light beers has led brewers to innovate by developing light beer. However, these products are not widely accepted in Europe compared to North America and Australasia because of their lack of fullness in the taste and low bitterness compared with conventional beer. The lower levels of some important compounds, present in light beer, can explain these features since they are responsible for the characteristics of the beer. These include alcohol soluble proteins, oligosaccharides, glycerol, polyphenols, iso-α-acids, fusel alcohols and trihydroxy fatty acids. Light beer is produced by several methods, the most commonly used is the addition of glucoamylase to the wort before or during fermentation. This enzyme metabolizes residual carbohydrates (mainly dextrins) transforming them into fermentable sugars and reducing the caloric and alcohol content in this type of beer. Recently pilot studies have been carried out with genetically engineered yeast strains in which amylolytic genes are introduced into the yeast genome in order to metabolize carbohydrate residues. When introducing amylolytic genes, a better fermentability occurs although the fullness of flavor still becomes reduced.
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Affiliation(s)
- Carlos A Blanco
- Dpto. Ingeniería Agrícola y Forestal (Área de Tecnología de los Alimentos), E.T.S. Ingenierías Agrarias, Universidad de Valladolid , Palencia , Spain
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van Zyl WH, Bloom M, Viktor MJ. Engineering yeasts for raw starch conversion. Appl Microbiol Biotechnol 2012; 95:1377-88. [PMID: 22797599 DOI: 10.1007/s00253-012-4248-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/12/2012] [Accepted: 06/14/2012] [Indexed: 11/29/2022]
Abstract
Next to cellulose, starch is the most abundant hexose polymer in plants, an import food and feed source and a preferred substrate for the production of many industrial products. Efficient starch hydrolysis requires the activities of both α-1,4 and α-1,6-debranching hydrolases, such as endo-amylases, exo-amylases, debranching enzymes, and transferases. Although amylases are widely distributed in nature, only about 10 % of amylolytic enzymes are able to hydrolyse raw or unmodified starch, with a combination of α-amylases and glucoamylases as minimum requirement for the complete hydrolysis of raw starch. The cost-effective conversion of raw starch for the production of biofuels and other important by-products requires the expression of starch-hydrolysing enzymes in a fermenting yeast strain to achieve liquefaction, hydrolysis, and fermentation (Consolidated Bioprocessing, CBP) by a single organism. The status of engineering amylolytic activities into Saccharomyces cerevisiae as fermentative host is highlighted and progress as well as challenges towards a true CBP organism for raw starch is discussed. Conversion of raw starch by yeast secreting or displaying α-amylases and glucoamylases on their surface has been demonstrated, although not at high starch loading or conversion rates that will be economically viable on industrial scale. Once efficient conversion of raw starch can be demonstrated at commercial level, engineering of yeast to utilize alternative substrates and produce alternative chemicals as part of a sustainable biorefinery can be pursued to ensure the rightful place of starch converting yeasts in the envisaged bio-economy of the future.
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Affiliation(s)
- W H van Zyl
- Department of Microbiology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa.
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Stable expression of barley α-amylase in S. cerevisiae for conversion of starch into bioethanol. Biochem Eng J 2012. [DOI: 10.1016/j.bej.2012.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Codon-optimized glucoamylase sGAI of Aspergillus awamori improves starch utilization in an industrial yeast. Appl Microbiol Biotechnol 2012; 95:957-68. [PMID: 22450569 DOI: 10.1007/s00253-012-4001-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 02/29/2012] [Accepted: 02/29/2012] [Indexed: 10/28/2022]
Abstract
The development of a yeast that converts raw starch to ethanol in one step (called consolidated bioprocessing) could yield large cost reductions in the bioethanol industry. The aim of this study was to develop an efficient amylolytic Saccharomyces cerevisiae strain suitable for industrial bioethanol production. A native and codon-optimized variant of the Aspergillus awamori glucoamylase gene were expressed in the S. cerevisiae Y294 laboratory strain. Codon optimization resulted to be effective and the synthetic sequence sGAI was then δ-integrated into a S. cerevisiae strain with promising industrial fermentative traits. The mitotically stable recombinant strains showed high enzymatic capabilities both on soluble and raw starch (2425 and 1140 nkat/g dry cell weight, respectively). On raw corn starch, the engineered yeasts exhibited improved fermentative performance with an ethanol yield of 0.42 (g/g), corresponding to 75 % of the theoretical maximum yield.
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Development of strains of the thermotolerant yeast Hansenula polymorpha capable of alcoholic fermentation of starch and xylan. Metab Eng 2009; 11:234-42. [DOI: 10.1016/j.ymben.2009.04.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2008] [Revised: 03/18/2009] [Accepted: 04/10/2009] [Indexed: 11/18/2022]
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Liu Z, Zhang G, Sun Y. Mutagenizing brewing yeast strain for improving fermentation property of beer. J Biosci Bioeng 2008; 106:33-8. [DOI: 10.1263/jbb.106.33] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 04/03/2008] [Indexed: 11/17/2022]
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Stable expression of glucoamylase gene in industrial strain ofSaccharomyces pastorianus with less diacetyl produced. ANN MICROBIOL 2007. [DOI: 10.1007/bf03175212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Ghang DM, Yu L, Lim MH, Ko HM, Im SY, Lee HB, Bai S. Efficient one-step starch utilization by industrial strains of Saccharomyces cerevisiae expressing the glucoamylase and α-amylase genes from Debaryomyces occidentalis. Biotechnol Lett 2007; 29:1203-8. [PMID: 17505783 DOI: 10.1007/s10529-007-9371-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Accepted: 03/08/2007] [Indexed: 11/30/2022]
Abstract
Amylolytic industrial polyploid strains of Saccharomyces cerevisiae (ATCC 4126, ATCC 9763 and ATCC 24858) expressing a glucoamylase gene (GAM1) or an alpha-amylase gene (AMY) from Debaryomyces occidentalis were developed. The glucoamylase activity of S. cerevisiae ATCC 9763 expressing the GAM1 gene was 3.7-times higher than that of D. occidentalis. On the other hand, alpha-amylase activity in the corresponding strain expressing the D. occidentalis AMY gene increased 10-times relative to D. occidentalis. These two recombinant yeast strains expressing the GAM1 gene and AMY gene, respectively were cultured simultaneously to produce both glucoamylase and alpha-amylase for efficient one-step utilization of starch. Growth, substrate utilization and enzyme activity of these strains are described.
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Affiliation(s)
- Dong-Myeong Ghang
- Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, 500-757, Korea
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Liu Z, Zhang G, Liu S. Constructing an amylolytic brewing yeast Saccharomyces pastorianus suitable for accelerated brewing. J Biosci Bioeng 2004; 98:414-9. [PMID: 16233729 DOI: 10.1016/s1389-1723(05)00305-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2004] [Accepted: 08/27/2004] [Indexed: 10/25/2022]
Abstract
An amylolytic brewing yeast Saccharomyces pastorianus, free of vector sequences and drug-resistance genes, was constructed by disrupting the alpha-acetolactate synthase gene and introducing the alpha-amylase gene as a selective marker. The resulting recombinant strain was able to utilize starch as the sole carbon source and its alpha-acetolactate synthase activity was lowered by 30%. Fermentation tests confirmed that the diacetyl concentration and the residual oligosaccharide were reduced by 70% and 25%, respectively, in fermented wort by the recombinant strain, while the brewing performance of the recombinant strain was retained.
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Affiliation(s)
- Zengran Liu
- Bioscience and Bioengineering College, Hebei Economics and Business University, 47 Xuefu Road, Shijiazhuang 050061, PR China
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