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Chen X, Pan B, Yu L, Wang B, Pan L. Enhancement of protein production in Aspergillus niger by engineering the antioxidant defense metabolism. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2024; 17:91. [PMID: 38951910 PMCID: PMC11218396 DOI: 10.1186/s13068-024-02542-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Accepted: 06/20/2024] [Indexed: 07/03/2024]
Abstract
BACKGROUND Research on protein production holds significant importance in the advancement of food technology, agriculture, pharmaceuticals, and bioenergy. Aspergillus niger stands out as an ideal microbial cell factory for the production of food-grade proteins, owing to its robust protein secretion capacity and excellent safety profile. However, the extensive oxidative folding of proteins within the endoplasmic reticulum (ER) triggers ER stress, consequently leading to protein misfolding reactions. This stressful phenomenon results in the accelerated generation of reactive oxygen species (ROS), thereby inducing oxidative stress. The accumulation of ROS can adversely affect intracellular DNA, proteins, and lipids. RESULT In this study, we enhanced the detoxification of ROS in A. niger (SH-1) by integrating multiple modules, including the NADPH regeneration engineering module, the glutaredoxin system, the GSH synthesis engineering module, and the transcription factor module. We assessed the intracellular ROS levels, growth under stress conditions, protein production levels, and intracellular GSH content. Our findings revealed that the overexpression of Glr1 in the glutaredoxin system exhibited significant efficacy across various parameters. Specifically, it reduced the intracellular ROS levels in A. niger by 50%, boosted glucoamylase enzyme activity by 243%, and increased total protein secretion by 88%. CONCLUSION The results indicate that moderate modulation of intracellular redox conditions can enhance overall protein output. In conclusion, we present a strategy for augmenting protein production in A. niger and propose a potential approach for optimizing microbial protein production system.
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Affiliation(s)
- Xin Chen
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, 510006, China
| | - Baoxiang Pan
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, 510006, China
| | - Leyi Yu
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, 510006, China
| | - Bin Wang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, 510006, China
| | - Li Pan
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, 510006, China.
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Zhu Y, Liu T, Wang Y, Chen G, Fang X, Zhou G, Wang J. ChsA, a Class Ⅱ Chitin Synthase, Contributes to Asexual Conidiation, Mycelial Morphology, Cell Wall Integrity, and the Production of Enzymes and Organic Acids in Aspergillus niger. J Fungi (Basel) 2023; 9:801. [PMID: 37623572 PMCID: PMC10455844 DOI: 10.3390/jof9080801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/24/2023] [Accepted: 07/25/2023] [Indexed: 08/26/2023] Open
Abstract
Chitin synthases (CHSs) are vital enzymes for the synthesis of chitin and play important and differential roles in fungal development, cell wall integrity, environmental adaptation, virulence, and metabolism in fungi. However, except for ChsC, a class III CHS, little is known about the functions of CHSs in Aspergillus niger, an important fungus that is widely applied in the fermentation industry and food processing, as well as a spoilage fungus of food and a human pathogen. This study showed the important functions of ChsA, a class II CHS, in A. niger using multi-phenotypic and transcriptional analyses under various conditions. The deletion of chsA led to severe defects in conidiation on different media and resulted in the formation of smaller and less compact pellets with less septa in hyphal cells during submerged fermentation. Compared with the WT, the ΔchsA mutants exhibited less chitin content, reduced growth under the stresses of cell wall-disturbing and oxidative agents, more released protoplasts, a thicker conidial wall, decreased production of amylases, pectinases, cellulases, and malic acid, and increased citric acid production. However, ΔchsA mutants displayed insignificant changes in their sensitivity to osmotic agents and infection ability on apple. These findings concurred with the alteration in the transcript levels and enzymatic activities of some phenotype-related genes. Conclusively, ChsA is important for cell wall integrity and mycelial morphology, and acts as a positive regulator of conidiation, cellular responses to oxidative stresses, and the production of malic acid and some enzymes, but negatively regulates the citric acid production in A. niger.
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Affiliation(s)
- Yunqi Zhu
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Science, South China Agricultural University, Guangzhou 510642, China; (Y.Z.); (T.L.); (G.C.); (X.F.)
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, China;
| | - Tong Liu
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Science, South China Agricultural University, Guangzhou 510642, China; (Y.Z.); (T.L.); (G.C.); (X.F.)
| | - Yingsi Wang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, China;
| | - Guojun Chen
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Science, South China Agricultural University, Guangzhou 510642, China; (Y.Z.); (T.L.); (G.C.); (X.F.)
| | - Xiang Fang
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Science, South China Agricultural University, Guangzhou 510642, China; (Y.Z.); (T.L.); (G.C.); (X.F.)
| | - Gang Zhou
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, China;
| | - Jie Wang
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Science, South China Agricultural University, Guangzhou 510642, China; (Y.Z.); (T.L.); (G.C.); (X.F.)
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Danner C, Mach RL, Mach-Aigner AR. The phenomenon of strain degeneration in biotechnologically relevant fungi. Appl Microbiol Biotechnol 2023:10.1007/s00253-023-12615-z. [PMID: 37341752 DOI: 10.1007/s00253-023-12615-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 05/26/2023] [Accepted: 05/31/2023] [Indexed: 06/22/2023]
Abstract
Fungi are widely exploited for large-scale production in the biotechnological industry to produce a diverse range of substances due to their versatility and relative ease of growing on various substrates. The occurrence of a phenomenon-the so-called fungal strain degeneration-leads to the spontaneous loss or decline of production capacity and results in an economic loss on a tremendous scale. Some of the most commonly applied genera of fungi in the biotechnical industry, such as Aspergillus, Trichoderma, and Penicillium, are threatened by this phenomenon. Although fungal degeneration has been known for almost a century, the phenomenon and its underlying mechanisms still need to be understood. The proposed mechanisms causing fungi to degenerate can be of genetic or epigenetic origin. Other factors, such as culture conditions, stress, or aging, were also reported to have an influence. This mini-review addresses the topic of fungal degeneration by describing examples of productivity losses in biotechnical processes using Aspergillus niger, Aspergillus oryzae, Trichoderma reesei, and Penicillium chrysogenum. Further, potential reasons, circumvention, and prevention methods are discussed. This is the first mini-review which provides a comprehensive overview on this phenomenon in biotechnologically used fungi, and it also includes a collection of strategies that can be useful to minimize economic losses which can arise from strain degeneration. KEY POINTS: • Spontaneous loss of productivity is evident in many fungi used in biotechnology. • The properties and mechanisms underlying this phenomenon are very versatile. • Only studying these underlying mechanisms enables the design of a tailored solution.
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Affiliation(s)
- Caroline Danner
- Christian Doppler Laboratory for Optimized Expression of Carbohydrate-Active Enzymes, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Gumpendorfer Str. 1a, 1060, Vienna, Austria
| | - Robert L Mach
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Gumpendorfer Str. 1a, 1060, Vienna, Austria
| | - Astrid R Mach-Aigner
- Christian Doppler Laboratory for Optimized Expression of Carbohydrate-Active Enzymes, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Gumpendorfer Str. 1a, 1060, Vienna, Austria.
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Gumpendorfer Str. 1a, 1060, Vienna, Austria.
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García-Cabrera RI, Valdez-Cruz NA, Blancas-Cabrera A, Trujillo-Roldán MA. Oxygen transfer rate affect polyhydroxybutyrate production and oxidative stress response in submerged cultures of Rhizobium phaseoli. Biochem Eng J 2020. [DOI: 10.1016/j.bej.2020.107721] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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5
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Chen H, Cao X, Zhu N, Jiang L, Zhang X, He Q, Wei P. A stepwise control strategy for glutathione synthesis in Saccharomyces cerevisiae based on oxidative stress and energy metabolism. World J Microbiol Biotechnol 2020; 36:117. [PMID: 32676694 DOI: 10.1007/s11274-020-02895-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 07/12/2020] [Indexed: 11/30/2022]
Abstract
A stepwise control strategy for enhancing glutathione (GSH) synthesis in yeast based on oxidative stress and energy metabolism was investigated. First, molasses and corn steep liquor were selected and fed as carbon source mixture at a flow rate of 1.5 g/L/h and 0.4 g/L/h, respectively, for increasing cell density in a 10 L fermenter. When the biomass reached 90 g/L, the KMnO4 sustained-release particles, composed of 1.5% KMnO4, 3% stearic acid, 2% polyethylene glycol and 3% agar powder, were prepared and added to the fermentation broth for maintaining the oxidative stress. The results showed that the maximum GSH accumulation of the group fed KMnO4 sustained-release particles was 39.0% higher than that of KMnO4-fed group. In addition to the improved average GSH productivity and average specific production rate, the activities of GSH peroxidase, γ-glutamylcysteine synthetase and GSH reductase, enzymes taking part in GSH metabolism, were also significantly enhanced by KMnO4 sustained-release particles feeding. Finally, 6 g/L sodium citrate fed as an energy adjuvant elevated the intracellular ATP level for further enhancing GSH production. Through the above stepwise strategy, the GSH accumulation reached 5.76 g/L, which was 2.84-fold higher than that of the control group. The stepwise control strategy based on oxidative stress and energy metabolism significantly improved GSH accumulation in yeast.
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Affiliation(s)
- Hailong Chen
- Jiangsu Key Laboratory of Chiral Pharmaceuticals Biosynthesis, College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, 93 Ji Chuan Road, Taizhou, 225300, People's Republic of China.
| | - Xitao Cao
- College of Biotechnology, Jiangsu University of Science and Technology, Sibaidu, Zhenjiang, 212018, People's Republic of China
| | - Nianqing Zhu
- Jiangsu Key Laboratory of Chiral Pharmaceuticals Biosynthesis, College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, 93 Ji Chuan Road, Taizhou, 225300, People's Republic of China
| | - Lihua Jiang
- Jiangsu Key Laboratory of Chiral Pharmaceuticals Biosynthesis, College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, 93 Ji Chuan Road, Taizhou, 225300, People's Republic of China
| | - Xiaoge Zhang
- Jiangsu Key Laboratory of Chiral Pharmaceuticals Biosynthesis, College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, 93 Ji Chuan Road, Taizhou, 225300, People's Republic of China
| | - Qingming He
- Jiangsu Key Laboratory of Chiral Pharmaceuticals Biosynthesis, College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, 93 Ji Chuan Road, Taizhou, 225300, People's Republic of China
| | - Pinghe Wei
- Jiangsu Key Laboratory of Chiral Pharmaceuticals Biosynthesis, College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, 93 Ji Chuan Road, Taizhou, 225300, People's Republic of China
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Ünlü AE, Takaç S. Improvement of superoxide dismutase activity using experimental design and radical promoters. BIOTECHNOL BIOTEC EQ 2017. [DOI: 10.1080/13102818.2017.1353923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- Ayşe Ezgi Ünlü
- Department of Chemical Engineering, Faculty of Engineering, Ankara University, Ankara, Turkey
| | - Serpil Takaç
- Department of Chemical Engineering, Faculty of Engineering, Ankara University, Ankara, Turkey
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7
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Roukas T. The role of oxidative stress on carotene production by Blakeslea trispora in submerged fermentation. Crit Rev Biotechnol 2015; 36:424-33. [PMID: 25600464 DOI: 10.3109/07388551.2014.989424] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In aerobic metabolism, reactive oxygen species (ROS) are formed during the fermentation that can cause oxidative stress in microorganisms. Microbial cells possess both enzymatic and non-enzymatic defensive systems that may protect cells from oxidative damage. The antioxidant enzymes superoxide dismutase and catalase are the two key defensive enzymes to oxidative stress. The factors that induce oxidative stress in microorganisms include butylated hydroxytoluene (BHT), hydrogen peroxide, metal ions, dissolved oxygen tension, elevated temperature, menadione, junglone, paraquat, liquid paraffin, introduction to bioreactors of shake flask inocula and synthetic medium sterilized at initial pH 11.0. Carotenes are highly unsaturated isoprene derivatives. They are used as antioxidants and as coloring agents for food products. In fungi, carotenes are derived via the mevalonate biosynthesis pathway. The key genes in carotene biosynthesis are hmgR, ipi, isoA, carG, carRA and carB. Among microorganisms, Βlakeslea trispora is the main microorganism used for the production of carotenes on the industrial scale. Currently, the synthetic medium is considered the superior substrate for the production of carotenes in a pilot plant scale. The fermentation systems used for the production of carotenes include shake flasks, stirred tank fermentor, bubble column reactor and flat panel photobioreactor. This review summarizes the oxidative stresses in microorganisms and it is focused on the current status of carotene production by B. trispora including oxidative stress induced by BHT, enhanced dissolved oxygen levels, iron ions, liquid paraffin and synthetic medium sterilized at an initial pH 11.0. The oxidative stress induced by the above factors increases significantly the production of carotenes. However, to further reduce the cost of carotene production, new biotechnological methods with higher productivity still need to be explored.
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Affiliation(s)
- Triantafyllos Roukas
- a Laboratory of Food Engineering and Processing, Department of Food Science and Technology , Aristotle University , Thessaloniki , Greece
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8
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Abrashev R, Stoitsova S, Krumova E, Pashova S, Paunova-Krasteva T, Vassilev S, Dolashka-Angelova P, Angelova M. Temperature-stress tolerance of the fungal strain Aspergillus niger 26: physiological and ultrastructural changes. World J Microbiol Biotechnol 2013; 30:1661-8. [DOI: 10.1007/s11274-013-1586-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 12/16/2013] [Indexed: 11/30/2022]
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9
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Gómez Sánchez C, Martínez-Trujillo A, Aguilar Osorio G. Oxygen transfer coefficient and the kinetic parameters of exo-polygalacturonase production byAspergillus flavipesFP-500 in shake flasks and bioreactor. Lett Appl Microbiol 2012; 55:444-52. [DOI: 10.1111/j.1472-765x.2012.03313.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 09/10/2012] [Accepted: 09/11/2012] [Indexed: 11/30/2022]
Affiliation(s)
- C.E. Gómez Sánchez
- Department of Food Science and Biotechnology; Faculty of Chemistry; National University of México; Ciudad Universitaria México
| | - A. Martínez-Trujillo
- Chemical and Biochemical Engineering Division; Technologic Institute of Higher Studies of Ecatepec; Ecatepec México
| | - G. Aguilar Osorio
- Department of Food Science and Biotechnology; Faculty of Chemistry; National University of México; Ciudad Universitaria México
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10
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Nanou K, Roukas T. Stimulation of the biosynthesis of carotenes by oxidative stress in Blakeslea trispora induced by elevated dissolved oxygen levels in the culture medium. BIORESOURCE TECHNOLOGY 2011; 102:8159-8164. [PMID: 21708460 DOI: 10.1016/j.biortech.2011.06.027] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 06/05/2011] [Accepted: 06/06/2011] [Indexed: 05/31/2023]
Abstract
The adaptive response of the fungus Blakeslea trispora to the oxidative stress induced by elevated dissolved oxygen concentrations during carotene production was investigated by measuring the specific activities of catalase (CAT) and superoxide dismutase (SOD) and the micromorphology of the fungus using a computerized image analysis system. Changes in the ratio of the volume of air (V(a)) over the medium and the volume of medium (V(m)) in the flask caused changes of the morphology of microorganism from clumps to pellets and increases in the specific activities of CAT and SOD. The oxidative stress in B. trispora resulted in a significant increase in carotene production, and a maximum proportion of β-carotene (60%), γ-carotene (50%), and lycopene (10%) (as percentages of total carotenes) was observed at a ratio V(a)/V(m) of 15.7, 4.0 and 1.5, respectively. The highest concentration of carotenes (115.0mg/g dry biomass) was obtained in V(a)/V(m) ratio of 9.0.
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Affiliation(s)
- Konstantina Nanou
- Department of Food Science and Technology, Aristotle University, Box 250, 54124 Thessaloniki, Greece
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11
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Oxidative stress and morphological changes in Blakeslea trispora induced by enhanced aeration during carotene production in a bubble column reactor. Biochem Eng J 2011. [DOI: 10.1016/j.bej.2011.02.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Abstract
Fungi are amongst the most industrially important microorganisms in current use within the biotechnology industry. Most such fungal cultures are highly aerobic in nature, a character that has been frequently referred to in both reactor design and fungal physiology. The most fundamentally significant outcome of the highly aerobic growth environment in fermenter vessels is the need for the fungal culture to effectively combat in the intracellular environment the negative consequences of high oxygen transfer rates. The use of oxygen as the respiratory substrate is frequently reported to lead to the development of oxidative stress, mainly due to oxygen-derived free radicals, which are collectively termed as reactive oxygen species (ROS). Recently, there has been extensive research on the occurrence, extent, and consequences of oxidative stress in microorganisms, and the underlying mechanisms through which cells prevent and repair the damage caused by ROS. In the present study, we critically review the current understanding of oxidative stress events in industrially relevant fungi. The review first describes the current state of knowledge of ROS concisely, and then the various antioxidant strategies employed by fungal cells to counteract the deleterious effects, together with their implications in fungal bioprocessing are also discussed. Finally, some recommendations for further research are made.
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Affiliation(s)
- Qiang Li
- Strathclyde Fermentation Centre, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
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13
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Liang G, Du G, Chen J. Salt-induced osmotic stress for glutathione overproduction in Candida utilis. Enzyme Microb Technol 2009. [DOI: 10.1016/j.enzmictec.2009.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Liang G, Liao X, Du G, Chen J. A new strategy to enhance glutathione production by multiple H2O2 induced oxidative stresses in Candida utilis. BIORESOURCE TECHNOLOGY 2009; 100:350-355. [PMID: 18650087 DOI: 10.1016/j.biortech.2008.06.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 06/07/2008] [Accepted: 06/10/2008] [Indexed: 05/26/2023]
Abstract
Effect of H(2)O(2)-induced oxidative stress on glutathione (GSH) production in Candida utilis was investigated. Based on the results that H(2)O(2) can effectively stimulate GSH accumulation but inhibit cell growth simultaneously, a novel strategy of multiple H(2)O(2) stresses with different concentrations (1 mmol/L at 4h, 2 mmol/L at 8h, and 4 mmol/L at 12h) were developed to maximize GSH production. As a result, a maximal GSH yield of 218 mg/L was achieved and a corresponding intracellular GSH content was 2.15%, which were 54.6% and 58.1% higher than the control. By further applying this strategy to 7 L fermentor, GSH yield and intracellular GSH content were 328 mg/L and 2.30%. Moreover, increased activities of catalase (CAT) and GSH reductase (GR) indicated that GSH and CAT were directly involved in protecting cell against oxidative stress by H(2)O(2).
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Affiliation(s)
- Guobin Liang
- School of Biotechnology, Jiangnan University, Wuxi, China
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15
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Abstract
It has been known for many years that oxygen (O2) may have toxic effects on aerobically growing microorganisms, mainly due to the threat arising from reactive oxygen species (ROS). In submerged culture industrial fermentation processes, maintenance of adequate levels of O2 (usually measured as dissolved oxygen tension (DOT)) can often be critical to the success of the manufacturing process. In viscous cultures of filamentous cultures, actively respiring, supplying adequate levels of O2 to the cultures by conventional air sparging is difficult and various strategies have been adopted to improve or enhance O2 transfer. However, adoption of those strategies to maintain adequate levels of DOT, that is, to avoid O2 limitation, may expose the fungi to potential oxidative damage caused by enhanced flux through the respiratory system. In the past, there have been numerous studies investigating the effects of DOT on fungal bioprocesses. Generally, in these studies moderately enhanced levels of O2 supply resulted in improvement in growth, product formation and acceptable morphological changes, while the negative impact of higher levels of DOT on morphology and product synthesis were generally assumed to be a consequence of "oxidative stress." However, very little research has actually been focused on investigation of this implicit link, and the mechanisms by which such effects might be mediated within industrial fungal processes. To elucidate this neglected topic, this review first surveys the basic knowledge of the chemistry of ROS, defensive systems in fungi and the effects of DOT on fungal growth, metabolism and morphology. The physiological responses of fungal cells to oxidative stress imposed by artificial and endogenous stressors are then critically reviewed. It is clear that fungi have a range of methods available to minimize the negative impacts of elevated ROS, but also that development of the various defensive systems or responses, can itself have profound consequences upon many process-related parameters. It is also clear that many of the practically convenient and widely used experimental methods of simulating oxidative stress, for example, addition of exogenous menadione or hydrogen peroxide, have effects on fungal cultures quite distinct from the effects of elevated levels of O2, and care must thus be exercised in the interpretation of results from such studies. The review critically evaluates our current understanding of the responses of fungal cultures to elevated O2 levels, and highlights key areas requiring further research to remedy gaps in knowledge.
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Affiliation(s)
- Zhonghu Bai
- Strathclyde Fermentation Center, Department of Bioscience, Strathclyde University, Glasgow, UK
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16
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Li Q, Harvey LM, McNeil B. Oxygen enrichment effects on protein oxidation, proteolytic activity and the energy status of submerged batch cultures of Aspergillus niger B1-D. Process Biochem 2008. [DOI: 10.1016/j.procbio.2007.11.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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17
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Nanou K, Roukas T, Kotzekidou P. Role of hydrolytic enzymes and oxidative stress in autolysis and morphology of Blakeslea trispora during β-carotene production in submerged fermentation. Appl Microbiol Biotechnol 2007; 74:447-53. [PMID: 17103162 DOI: 10.1007/s00253-006-0666-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Revised: 08/23/2006] [Accepted: 09/05/2006] [Indexed: 11/28/2022]
Abstract
The role of hydrolytic enzymes (proteases and chitinase) and oxidative stress in the autolysis and morphology of Blakeslea trispora during beta-carotene production from a chemically defined medium in shake flask culture was investigated. The process of cellular autolysis was studied by measuring the changes in biomass dry weight, pH, concentration of beta-carotene, specific activity of the hydrolytic enzymes and micromorphology of the fungus using a computerized image analysis system. In addition, the phenomenon of autolysis was associated with high concentrations of reactive oxygen species (ROS). The accumulation of ROS produced during fermentation causes oxidative stress in B. trispora. Oxidative stress was examined in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). The profile of the specific activities of the above enzymes appeared to correlate with the oxidative stress of the fungus. The high activities of CAT and SOD showed that B. trispora is found under oxidative stress during beta-carotene production. The culture began to show signs of autolysis nearly in the growth phase and autolysis increased significantly during the production phase. The morphological differentiation of the fungus was a result of the degradation of the cell membrane by hydrolytic enzymes and oxidative stress. Increased beta-carotene production is correlated with intense autolysis of clumps, which has as a consequence the increase of the freely dispersed mycelia.
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Affiliation(s)
- K Nanou
- Department of Food Science and Technology, Aristotle University of Thessaloniki, Box 250, 54124 Thessaloniki, Greece
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Wang L, Ridgway D, Gu T, Moo-Young M. Bioprocessing strategies to improve heterologous protein production in filamentous fungal fermentations. Biotechnol Adv 2004; 23:115-29. [PMID: 15694123 DOI: 10.1016/j.biotechadv.2004.11.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2004] [Revised: 11/15/2004] [Accepted: 11/17/2004] [Indexed: 11/24/2022]
Abstract
Filamentous fungi have long been used for the production of metabolites and enzymes. With developments in genetic engineering and molecular biology, filamentous fungi have also achieved increased attention as hosts for recombinant DNA. However, the production levels of non-fungal proteins are usually low. Despite the achievements obtained using molecular tools, the heterologous protein loss caused by extracellular fungal protease degradation persists. This review provides an overview of the potential bioprocessing strategies that can be applied to inhibit protease activity thereby enhancing heterologous protein production.
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Affiliation(s)
- Liping Wang
- Department of Chemical Engineering, Ohio University, Athens, OH 45701, USA
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Abstract
Glutathione (GSH; gamma-L-glutamyl-L-cysteinyl-glycine), a non-protein thiol with a very low redox potential (E'0 = 240 mV for thiol-disulfide exchange), is present in high concentration up to 10 mM in yeasts and filamentous fungi. GSH is concerned with basic cellular functions as well as the maintenance of mitochondrial structure, membrane integrity, and in cell differentiation and development. GSH plays key roles in the response to several stress situations in fungi. For example, GSH is an important antioxidant molecule, which reacts non-enzymatically with a series of reactive oxygen species. In addition, the response to oxidative stress also involves GSH biosynthesis enzymes, NADPH-dependent GSH-regenerating reductase, glutathione S-transferase along with peroxide-eliminating glutathione peroxidase and glutaredoxins. Some components of the GSH-dependent antioxidative defence system confer resistance against heat shock and osmotic stress. Formation of protein-SSG mixed disulfides results in protection against desiccation-induced oxidative injuries in lichens. Intracellular GSH and GSH-derived phytochelatins hinder the progression of heavy metal-initiated cell injuries by chelating and sequestering the metal ions themselves and/or by eliminating reactive oxygen species. In fungi, GSH is mobilized to ensure cellular maintenance under sulfur or nitrogen starvation. Moreover, adaptation to carbon deprivation stress results in an increased tolerance to oxidative stress, which involves the induction of GSH-dependent elements of the antioxidant defence system. GSH-dependent detoxification processes concern the elimination of toxic endogenous metabolites, such as excess formaldehyde produced during the growth of the methylotrophic yeasts, by formaldehyde dehydrogenase and methylglyoxal, a by-product of glycolysis, by the glyoxalase pathway. Detoxification of xenobiotics, such as halogenated aromatic and alkylating agents, relies on glutathione S-transferases. In yeast, these enzymes may participate in the elimination of toxic intermediates that accumulate in stationary phase and/or act in a similar fashion as heat shock proteins. GSH S-conjugates may also form in a glutathione S-transferases-independent way, e.g. through chemical reaction between GSH and the antifugal agent Thiram. GSH-dependent detoxification of penicillin side-chain precursors was shown in Penicillium sp. GSH controls aging and autolysis in several fungal species, and possesses an anti-apoptotic feature.
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Affiliation(s)
- István Pócsi
- Department of Microbiology and Biotechnology, Faculty of Sciences, University of Debrecen, P.O. Box 63, H-4010 Debrecen, Hungary
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Bai Z, Harvey LM, McNeil B. Elevated temperature effects on the oxidant/antioxidant balance in submerged batch cultures of the filamentous fungus Aspergillus niger B1-D. Biotechnol Bioeng 2003; 83:772-9. [PMID: 12889017 DOI: 10.1002/bit.10726] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In the present study the relationship between oxidative stress and elevated culture temperature was examined in an industrially relevant fungal culture, Aspergillus niger B1-D. For the first time, both the intracellular levels of the main stressor species (superoxide radical [O(2) (.-)]) and activities of cellular defensive enzymes (superoxide dismutase [SOD], catalase [CAT], and glutathione peroxide [GPx]) were quantified at varying temperature (25, 30, 35, 40 degrees C) to more fully characterize culture response in different growth phases. Elevated culture temperature led to increased O(2) (.-) levels in various culture phases. In the exponential phase this was due to an enhanced generation of O(2) (.-), whereas in stationary phase a decreased dismutation rate may also have contributed. CAT activities generally increased with culture temperature, whereas GPx activity changed little as temperature rose, indicating that GPx played only a minor role in destroying H(2)O(2) in this A. niger. The combination of elevated temperature (35 degrees C) and increased O(2) supply (50% enrichment) led to decreased levels of O(2) (.-) compared to the cultivation at 35 degrees C gassed with air, probably due to enhanced activity of the alternative fungal respiratory pathway. Our findings indicate that while elevated cultivation temperature does clearly induce oxidative stress events, mechanistically, it does so by a rather more complex route than previous studies indicate. Elevated temperature caused a marked disparity in the activities of SOD and CAT, very distinct from the integrated increase in activity of these enzymes in response to oxidative stress.
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Affiliation(s)
- Zhonghu Bai
- Strathclyde Fermentation Centre, Strathclyde University, Royal College Building, 204 George Street, Glasgow G1 1XW, Scotland, United Kingdom
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Sámi L, Karaffa L, Emri T, Pócsi I. Autolysis and ageing of Penicillium chrysogenum under carbon starvation: respiration and glucose oxidase production. Acta Microbiol Immunol Hung 2003; 50:67-76. [PMID: 12793202 DOI: 10.1556/amicr.50.2003.1.7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
During the exponential growth phase of Penicillium chrysogenum NCAIM 00237 the effective conversion of glucose and O2 to gluconate and H2O2 by glucose oxidase (GOX) was the most likely source of intracellular ROS measured. In glucose-supplemented autolysing cultures, the increased of intracellular ROS concentration was attributed to respiration in the absence of any significant GOX activity. The induction of GOX and catalase by glucose and H2O2 was clearly age-dependent in P. chrysogenum. In ageing cryptic growth phase cultures, superoxide dismutase and cyanide-resistant respiration were the major elements of antioxidative defence but these activities were insufficient to prevent the progressive accumulation of ROS and the concomitant decrease in cell vitality.
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Affiliation(s)
- L Sámi
- Department of Microbiology and Biotechnology, Faculty of Sciences, University of Debrecen, P.O. Box 63, H-4010 Debrecen, Hungary
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22
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Kreiner M, Harvey LM, McNeil B. Morphological and enzymatic responses of a recombinant Aspergillus niger to oxidative stressors in chemostat cultures. J Biotechnol 2003; 100:251-60. [PMID: 12443856 DOI: 10.1016/s0168-1656(02)00245-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Continuous chemostat cultures of a recombinant strain of Aspergillus niger (B1-D), engineered to produce the marker protein hen egg white lysozyme, were investigated with regard to their susceptibility to oxidative stress. The culture response to oxidative stress, produced either by addition of exogenous hydrogen peroxide (H(2)O(2)) or by high dissolved oxygen tension (DOT), was characterised in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). Since the morphology is so critical in submerged fungal bioprocesses, the key morphological indices were analysed using a semi-automated image analysis system. Both oxidant stressors, H(2)O(2) and elevated DOT, increased both enzyme activities, however, the extent was different: exogenous H(2)O(2) led mainly to increased CAT activity, whereas gassing with O(2) enriched air, which resulted in a DOT of 165% of air saturation, increased both enzyme activities more than 2-fold compared with the control steady state culture. Addition of exogenous H(2)O(2) resulted in shorter hyphae compared with control steady state cultures. These findings indicate that it is unsound to use exogenous H(2)O(2) to simulate oxidative stress induced by elevated dissolved oxygen levels since the response to each might be quite different, both in terms of enzymatic (defensive) responses and in terms of culture morphology.
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Affiliation(s)
- Michaela Kreiner
- Strathclyde Fermentation Centre, Royal College Building, University of Strathclyde, 204 George Street, G1 1XW Glasgow, UK
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Kreiner M, Harvey LM, McNeil B. Oxidative stress response of a recombinant Aspergillus niger to exogenous menadione and H2O2 addition. Enzyme Microb Technol 2002. [DOI: 10.1016/s0141-0229(01)00517-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bai Z, Harvey LM, McNeil B. Use of the chemiluminescent probe lucigenin to monitor the production of the superoxide anion radical in a recombinant Aspergillus niger (B1-D). Biotechnol Bioeng 2001; 75:204-11. [PMID: 11536143 DOI: 10.1002/bit.1180] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Direct detection of intracellular superoxide anion radical (O(2)(.-)) production is of critical importance for investigating the responses of filamentous fungi to oxidative stress in bioprocesses. The purpose of this study is to establish a reliable method to monitor the O(2)(.-) production within pellets of Aspergillus niger. Addition of pure oxygen and the redox cycling agent paraquat to fungal pellet suspensions resulted in a considerable increase in lucigenin-derived chemiluminescence (LDCL). In the presence of exogenous superoxide dismutase (SOD), the LDCL of a disrupted cell solution was inhibited. In contrast, with addition of diethyldithiocarbamate and sodium azide, respectively, the inhibitors of Cu, Zn-SOD and Mn-SOD, an increased LDCL was observed. Further, as a probe, lucigenin can be absorbed and accumulated in fungal pellet within a few minutes. Various pretreatments of the bioreactor sample for the measurement of LDCL, were also investigated in the present study, and the use of intact pellets was adopted here rather than disrupting cells because the latter treatment led to difficulties in LDCL measurement. These results show that lucigenin may be used as a convenient chemiluminescent probe to monitor intracellular production of O(2)(.-) in filamentous fungi, and thus to follow changes in the level of this stressor within fungi
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Affiliation(s)
- Z Bai
- Strathclyde Fermentation Centre, Department of Bioscience and Biotechnology, Strathclyde University, 204 George Street, Glasgow G1 1XW, United Kingdom
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