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Yang S, Bai M, Kwok LY, Zhong Z, Sun Z. The intricate symbiotic relationship between lactic acid bacterial starters in the milk fermentation ecosystem. Crit Rev Food Sci Nutr 2023:1-18. [PMID: 37983125 DOI: 10.1080/10408398.2023.2280706] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Fermentation is one of the most effective methods of food preservation. Since ancient times, food has been fermented using lactic acid bacteria (LAB). Fermented milk is a very intricate fermentation ecosystem, and the microbial metabolism of fermented milk largely determines its metabolic properties. The two most frequently used dairy starter strains are Streptococcus thermophilus (S. thermophilus) and Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). To enhance both the culture growth rate and the flavor and quality of the fermented milk, it has long been customary to combine S. thermophilus and L. bulgaricus in milk fermentation due to their mutually beneficial and symbiotic relationship. On the one hand, the symbiotic relationship is reflected by the nutrient co-dependence of the two microbes at the metabolic level. On the other hand, more complex interaction mechanisms, such as quorum sensing between cells, are involved. This review summarizes the application of LAB in fermented dairy products and discusses the symbiotic mechanisms and interactions of milk LAB starter strains from the perspective of nutrient supply and intra- and interspecific quorum sensing. This review provides updated information and knowledge on microbial interactions in a fermented milk ecosystem.
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Affiliation(s)
- Shujuan Yang
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot, PR China
- Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot, PR China
- Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot, PR China
| | - Mei Bai
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot, PR China
- Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot, PR China
- Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot, PR China
| | - Lai-Yu Kwok
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot, PR China
- Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot, PR China
- Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot, PR China
| | - Zhi Zhong
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot, PR China
- Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot, PR China
- Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot, PR China
| | - Zhihong Sun
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot, PR China
- Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot, PR China
- Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot, PR China
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Dysin AP, Egorov AR, Godzishevskaya AA, Kirichuk AA, Tskhovrebov AG, Kritchenkov AS. Biologically Active Supplements Affecting Producer Microorganisms in Food Biotechnology: A Review. Molecules 2023; 28:molecules28031413. [PMID: 36771079 PMCID: PMC9921933 DOI: 10.3390/molecules28031413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 01/18/2023] [Accepted: 01/27/2023] [Indexed: 02/05/2023] Open
Abstract
Microorganisms, fermentation processes, and the resultant metabolic products are a key driving force in biotechnology and, in particular, in food biotechnology. The quantity and/or quality of final manufactured food products are directly related to the efficiency of the metabolic processes of producer microorganisms. Food BioTech companies are naturally interested in increasing the productivity of their biotechnological production lines. This could be achieved via either indirect or direct influence on the fundamental mechanisms governing biological processes occurring in microbial cells. This review considers an approach to improve the efficiency of producer microorganisms through the use of several types of substances or complexes affecting the metabolic processes of microbial producers that are of interest for food biotechnology, particularly fermented milk products. A classification of these supplements will be given, depending on their chemical nature (poly- and oligosaccharides; poly- and oligopeptides, individual amino acids; miscellaneous substances, including vitamins and other organic compounds, minerals, and multicomponent supplements), and the approved results of their application will be comprehensively surveyed.
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Affiliation(s)
- Artem P. Dysin
- Faculty of Science, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya St. 6, 117198 Moscow, Russia
| | - Anton R. Egorov
- Faculty of Science, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya St. 6, 117198 Moscow, Russia
| | - Anastasia A. Godzishevskaya
- Faculty of Science, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya St. 6, 117198 Moscow, Russia
| | - Anatoly A. Kirichuk
- Faculty of Science, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya St. 6, 117198 Moscow, Russia
| | - Alexander G. Tskhovrebov
- Faculty of Science, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya St. 6, 117198 Moscow, Russia
- Correspondence: (A.G.T.); (A.S.K.)
| | - Andreii S. Kritchenkov
- Faculty of Science, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya St. 6, 117198 Moscow, Russia
- Metal Physics Laboratory, Institute of Technical Acoustics NAS of Belarus, Ludnikova Prosp. 13, 210009 Vitebsk, Belarus
- Correspondence: (A.G.T.); (A.S.K.)
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Ayivi RD, Ibrahim SA. Lactic acid bacteria: An essential probiotic and starter culture for the production of yoghurt. Int J Food Sci Technol 2022. [DOI: 10.1111/ijfs.16076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Raphael D. Ayivi
- Department of Food and Nutritional Sciences North Carolina A&T State University Greensboro NC 27411 USA
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering University of North Carolina Greensboro NC 27412 USA
| | - Salam A. Ibrahim
- Department of Food and Nutritional Sciences North Carolina A&T State University Greensboro NC 27411 USA
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Zhou Y, Cui Y, Qu X. Comparative transcriptome analysis for the biosynthesis of antioxidant exopolysaccharide in Streptococcus thermophilus CS6. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2022; 102:5321-5332. [PMID: 35318677 DOI: 10.1002/jsfa.11886] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/21/2022] [Accepted: 03/22/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Food grade Streptococcus thermophilus produces biological exopolysaccharides (EPSs) with great potential with respect to catering for higher health-promoting demands; however, how S. thermophilus regulates the biosynthesis of EPS is not completely understood, decelerating the application of these polymers. In our previous study, maltose, soy peptone and initial pH were three key factors of enhancing EPS yield in S. thermophilus CS6. Therefore, we aimed to investigate the regulating mechanisms of EPS biosynthesis in S. thermophilus CS6 via the method of comparative transcriptome and differential carbohydrate metabolism. RESULTS Soy peptone addition (58.6 g L-1 ) and a moderate pH (6.5) contributed to a high bacterial biomass and a high EPS yield (407 mg L-1 ). Maltose, soy peptone and initial pH greatly influenced lactose utilization in CS6. Soy peptone addition induced a high accumulation of mannose and arabinose in intracellular CS6, differential monosaccharide composition (mannose, glucose and arabinose) in EPS and high radical [2,2-diphenyl-1-picrylhydrazyl, superoxide and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] scavenging activities. Carbohydrate transportation, sugar activation and eps cluster-associated genes were differentially expressed to regulate EPS biosynthesis. Correlation analysis indicated high production of EPSs depended on high expression of lacS, galPMKUTE, pgm, gt2-5&4-1 and epsLM. CONCLUSION The production of antioxidant EPS in S. thermophilus CS6 depended on the regulation of galactose metabolism cluster and eps cluster. The present study recommends a new approach for enhancing EPS production by transcriptomic regulation for further food and health application of EPS. © 2022 Society of Chemical Industry.
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Affiliation(s)
- Yang Zhou
- Department of Food Nutrition and Health, School of Medicine and Health, Harbin Institute of Technology, Harbin, China
| | - Yanhua Cui
- Department of Food Nutrition and Health, School of Medicine and Health, Harbin Institute of Technology, Harbin, China
| | - Xiaojun Qu
- Institute of Microbiology, Heilongjiang Academy of Sciences, Harbin, China
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Dushkova M, Kodinova S, Denkova Z, Yanakieva V, Menkov ND. Physicochemical, microbiological, and sensory characteristics of probiotic Bulgarian yoghurts obtained by ultrafiltration of goat's milk. ACTA ACUST UNITED AC 2021; 76:481-489. [PMID: 34147044 DOI: 10.1515/znc-2021-0064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 05/31/2021] [Indexed: 11/15/2022]
Abstract
The purpose of this study was to investigate the microbiological (number of viable lactic acid bacteria and bifidobacteria), physicochemical (dry matter, protein and fat contents, titratable acidity, and pH), and sensory characteristics (appearance of coagulum, taste and aroma, structure at cutting, color, and consistency at shattering) of probiotic Bulgarian yoghurts obtained by ultrafiltration of goat's milk. These yoghurts were obtained using volume reduction ratios of 2 and 3 with the probiotic starters MZ2f, MZ2f + Bifidobacterium bifidum BB - 87, and MZ2f + Lactobacillus acidophilus LAB - 8. The increase in the level of the concentration by ultrafiltration led to an increase in the dry matter, protein and fat contents of the yoghurts, in the number of lactic acid bacteria and titratable acidity, and to a decrease in the pH. The twofold concentration by ultrafiltration resulted in a higher number of lactic acid bacteria in comparison with yoghurts made without ultrafiltration, and with better sensory characteristics compared to yoghurts without and with threefold ultrafiltration. The higher number of viable cells and better sensory characteristics were obtained for yoghurts with MZ2f + Bifidobacterium bifidum BB - 87 and MZ2f + Lactobacillus acidophilus LAB - 8 in comparison with MZ2f alone.
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Affiliation(s)
- Mariya Dushkova
- Department of Process Engineering, University of Food Technologies Plovdiv, 26, Maritza Blvd., Plovdiv4000, Bulgaria
| | - Siyka Kodinova
- Department of Process Engineering, University of Food Technologies Plovdiv, 26, Maritza Blvd., Plovdiv4000, Bulgaria
| | - Zapryana Denkova
- Department of Microbiology, University of Food Technologies Plovdiv, Plovdiv, Bulgaria
| | - Velichka Yanakieva
- Department of Microbiology, University of Food Technologies Plovdiv, Plovdiv, Bulgaria
| | - Nikolay Dimitrov Menkov
- Department of Process Engineering, University of Food Technologies Plovdiv, 26, Maritza Blvd., Plovdiv4000, Bulgaria
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Gagliano MC, Sudmalis D, Pei R, Temmink H, Plugge CM. Microbial Community Drivers in Anaerobic Granulation at High Salinity. Front Microbiol 2020; 11:235. [PMID: 32174895 PMCID: PMC7054345 DOI: 10.3389/fmicb.2020.00235] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 01/31/2020] [Indexed: 01/24/2023] Open
Abstract
In the recent years anaerobic sludge granulation at elevated salinities in upflow anaerobic sludge blanket (UASB) reactors has been investigated in few engineering based studies, never addressing the microbial community structural role in driving aggregation and keeping granules stability. In this study, the combination of different techniques was applied in order to follow the microbial community members and their structural dynamics in granules formed at low (5 g/L Na+) and high (20 g/L Na+) salinity conditions. Experiments were carried out in four UASB reactors fed with synthetic wastewater, using two experimental set-ups. By applying 16S rRNA gene analysis, the comparison of granules grown at low and high salinity showed that acetotrophic Methanosaeta harundinacea was the dominant methanogen at both salinities, while the dominant bacteria changed. At 5 g/L Na+, cocci chains of Streptoccoccus were developing, while at 20 g/L Na+ members of the family Defluviitaleaceae formed long filaments. By means of Fluorescence in Situ Hybridization (FISH) and Scanning Electron Microscopy (SEM), it was shown that aggregation of Methanosaeta in compact clusters and the formation of filaments of Streptoccoccus and Defluviitaleaceae during the digestion time were the main drivers for the granulation at low and high salinity. Interestingly, when the complex protein substrate (tryptone) in the synthetic wastewater was substituted with single amino acids (proline, leucine and glutamic acid), granules at high salinity (20 g/L Na+) were not formed. This corresponded to a decrease of Methanosaeta relative abundance and a lack of compact clustering, together with disappearance of Defluviitaleaceae and consequent absence of bacterial filaments within the dispersed biomass. In these conditions, a biofilm was growing on the glass wall of the reactor instead, highlighting that a complex protein substrate such as tryptone can contribute to granules formation at elevated salinity.
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Affiliation(s)
- Maria Cristina Gagliano
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands.,Wetsus - European Centre of Excellence for Sustainable Water Technology, Leeuwarden, Netherlands
| | - Dainis Sudmalis
- Department of Environmental Technology, Wageningen University & Research, Wageningen, Netherlands
| | - Ruizhe Pei
- Wetsus - European Centre of Excellence for Sustainable Water Technology, Leeuwarden, Netherlands
| | - Hardy Temmink
- Wetsus - European Centre of Excellence for Sustainable Water Technology, Leeuwarden, Netherlands.,Department of Environmental Technology, Wageningen University & Research, Wageningen, Netherlands
| | - Caroline M Plugge
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands.,Wetsus - European Centre of Excellence for Sustainable Water Technology, Leeuwarden, Netherlands
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Leek-derived codoped carbon dots as efficient fluorescent probes for dichlorvos sensitive detection and cell multicolor imaging. Anal Bioanal Chem 2019; 411:7879-7887. [PMID: 31691847 DOI: 10.1007/s00216-019-02192-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Revised: 09/09/2019] [Accepted: 10/07/2019] [Indexed: 01/31/2023]
Abstract
A biomass nitrogen and sulfur codoped carbon dots (NS-Cdots) was prepared by a simple and clean hydrothermal method using leek, and was employed as efficient fluorescent probes for sensitive detection of organophosphorus pesticides (OPs). The leek-derived NS-Cdots emitted blue fluorescence, but was quenched by H2O2. Due to acetylcholinesterase/choline oxidase-based cascade enzymatic reaction that produces H2O2 and the inhibition effect of OPs on acetylcholinesterase activity, a NS-Cdots-based fluorescence "off-on" method to detect OPs-dichlorvos (DDVP) was developed. More sensitivity and wider linear detection range were achieved from 1.0 × 10-9 to 1.0 × 10-3 M (limit of detection = 5.0 × 10-10 M). This developed method was applied to the detection of DDVP in Chinese cabbage successfully. The average recoveries were in the range of 96.0~104.0% with a relative standard deviation of less than 3.3%. In addition, the NS-Cdots fluorescent probes were also employed successfully in multicolor imaging of living cells, manifesting that the NS-Cdots fluorescent probes have great application potential in agricultural and biomedical fields. Graphical Abstract.
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Effect of Greek-style yoghurt manufacturing processes on starter and probiotic bacteria populations during storage. Int Dairy J 2019. [DOI: 10.1016/j.idairyj.2019.02.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Sharma V, Kaur T, Bridle H, Ghosh M. Antimicrobial efficacy and safety of mucoadhesive exopolymer produced by Acinetobacter haemolyticus. Int J Biol Macromol 2016; 94:187-193. [PMID: 27720965 DOI: 10.1016/j.ijbiomac.2016.10.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 09/13/2016] [Accepted: 10/05/2016] [Indexed: 10/20/2022]
Abstract
This study evaluated five extracellular polymers of bacterial origin possessing mucoadhesive properties for their antimicrobial properties and toxicological characteristics. Of the five tested mucoadhesive biopolymers, the extracellular polymer produced by a strain of Acinetobacter haemolyticus exhibited broad antimicrobial efficacy towards Yersinia enterocolitica, Salmonella typhimurium, Listeria monocytogenes, Escherichia coli O157:H7 and Bacillus subtilis. Significant (p<0.05) inhibition of gram negative bacterial pathogens followed by gram positives were observed with the biopolymer at a dose of 40-60μg ml-1 at ambient temperature. The cytotoxicity under in vitro conditions and oral toxicity in murine models was also evaluated. The biopolymer did not elicit either haemolytic activity or toxicity in RAW 264.7 cell lines. Haemotological, histopathological and general examinations indicated no adverse effects in Swiss albino mice fed with the biopolymer (120mg kg-1 body weight-1 day1) over a period of 30 days. These results suggested that the biopolymer was well tolerated without any signs of toxicity and may have several potential biomedical applications where disinfection is desired.
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Affiliation(s)
- Vivek Sharma
- Department of Biotechnology, Thapar University, Patiala-147004, India
| | - Taranpreet Kaur
- Department of Biotechnology, Thapar University, Patiala-147004, India
| | - Helen Bridle
- Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, Scotland, United Kingdom
| | - Moushumi Ghosh
- Department of Biotechnology, Thapar University, Patiala-147004, India.
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Leroy F, De Vuyst L. Advances in production and simplified methods for recovery and quantification of exopolysaccharides for applications in food and health. J Dairy Sci 2016; 99:3229-3238. [PMID: 26874424 DOI: 10.3168/jds.2015-9936] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/26/2015] [Indexed: 01/20/2023]
Abstract
The capacity of strains to produce exopolysaccharides (EPS) is widespread among species of lactic acid bacteria and bifidobacteria, although the physiological role of these molecules is not yet clearly understood. When EPS are produced during food fermentation, they confer technological benefits on the fermented end products, such as improved texture and stability. In addition, some of these EPS may have beneficial effects on consumer health. These uses of EPS necessitate optimal and sufficient production of these molecules, both in situ and ex situ, not only to improve their yields but also to obtain a particular functionality. The present study reviews the commonly used methods of production, isolation, and quantification that have been used in recent studies dealing with EPS-producing lactic acid bacteria and bifidobacteria.
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Affiliation(s)
- Frédéric Leroy
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
| | - Luc De Vuyst
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
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Hagi T, Kobayashi M, Nomura M. Metabolome analysis of milk fermented by γ-aminobutyric acid–producing Lactococcus lactis. J Dairy Sci 2016; 99:994-1001. [DOI: 10.3168/jds.2015-9945] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/01/2015] [Indexed: 11/19/2022]
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Kebouchi M, Galia W, Genay M, Soligot C, Lecomte X, Awussi AA, Perrin C, Roux E, Dary-Mourot A, Le Roux Y. Implication of sortase-dependent proteins of Streptococcus thermophilus in adhesion to human intestinal epithelial cell lines and bile salt tolerance. Appl Microbiol Biotechnol 2016; 100:3667-79. [DOI: 10.1007/s00253-016-7322-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 01/10/2016] [Accepted: 01/13/2016] [Indexed: 01/06/2023]
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Characterization and upregulation of bifunctional phosphoglucomutase/phosphomannomutase enzyme in an exobiopolymer overproducing strain of Acinetobacter haemolyticus. Microbiol Res 2015; 181:8-14. [PMID: 26640047 DOI: 10.1016/j.micres.2015.08.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Revised: 07/13/2015] [Accepted: 08/04/2015] [Indexed: 11/24/2022]
Abstract
Several members of the Acinetobacter spp. produce exobiopolymer (EBP) of considerable biotechnological interest. In a previous study, we reported phosphate removal capacity of EBP produced by Acinetobacter haemolyticus. Insertional mutagenesis was attempted to develop EBP-overproducing strains of A. haemolyticus and mutant MG606 was isolated. In order to understand the underlying mechanism of overproduction, the EBP overproducing mutant MG606 was analyzed and compared with the wild type counterpart for its key EBP synthetic enzymes. The EBP produced by MG606 mutant was 650 mg/L compared to 220 mg/L in its wild type counterpart. Significantly high (p<0.05) levels of phosphoglucomutase/phosphomannomutase (PGM/PMM) in MG606 mutant was noted, whereas activities of other enzymes responsible for EBP synthesis showed no significant change (p>0.05). The up-regulation of PGM/PMM expression in mutant was further confirmed by real time reverse transcriptase (RT)-PCR of PGM/PMM transcripts. The optimal conditions for PGM/PMM activity were found to be 35 °C and pH 7.5; PGM/PMM activity was inhibited by ions such as lithium, zinc, nickel. Further, incubation of cells with a PGM inhibitor (lithium) resulted in a concentration-dependent decrease in EBP production further confirming the role of PGM/PMM overexpression in enhanced EBP production by the mutant. Overall the results of our study indicate a key role of PGM/PMM in enhanced EBP production, as evident from enhanced enzyme activity, increased PGM/PMM transcripts and reduction in EBP synthesis by a PGM inhibitor. We envisage a potential exploitation of the insights so obtained to effectively engineer strains of Acinetobacter for overproducing phosphate binding EBP.
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