Oenococcusoeni: The Main Lactic Acid Bacteria Involved in Wine-Making
Longxiang Liu1, Shuai Peng1, Hongyu Zhao1, Yun Wang1, Hua Li1,2,3* and Hua Wang1,2,3*
1Northwest A&F University, China
2Shaanxi Engineering Research Center for Viti-Viniculture, China
3Heyang Experimental and Demonstrational Stations for Grape, China
Submission: May 19, 2017; Published: June 30, 2017
*Corresponding author: Hua Li, College of Enology, Northwest A&F University, Shaanxi Engineering Research Center for Viti-Viniculture, Heyang Experimental and Demonstrational Stations for Grape, Yangling, Weinan, Shaanxi, 712100, China, Email: wanghua@nwsuaf.edu.cn
Hua Wang, College of Enology, Northwest A&F University, Shaanxi Engineering Research Center for Viti-Viniculture, Heyang Experimental and Demonstrational Stations for Grape, Yangling, Weinan, Shaanxi 712100, China, Email: naaz.27khan@gmail.com
How to cite this article:Longxiang L, Shuai P, Hongyu Z, Yun W. Oenococcusoeni: The Main Lactic Acid Bacteria Involved in Wine-Making. Adv Biotech & Micro. 004 2017; 4(2): 555628. DOI:10.19080/AIBM.2017.04.555628.
Abstract
Based on the research advances of our team, this article examines properties of the lactic bacteria-Oenococcusoeni. The genetic diversity are mainly in accordance with the result of fermentation properties, random amplified polymorphic, single-enzyme amplified fragment length polymorphism, multilocus sequence typing, pulsed-field gel electrophoresis and the genome-wide comparison analysis. The adaptive stress response is based on the condition of culture, membrane lipid composition and heterologous expression of genes from O. oeni. Biological properties focus on the probiotic properties of O.oeni, such as antioxidant activity, nutritional value and sanitarian function of wine after malo- lactic fermentation. And the bacteria reconstruction and preservation are also involved. The advice on the research directionis introduced in this article.
Keywords: Oenococcus oeni; Wine-making; Genetic diversity; Stress response; Biological properties; Bacteria reconstruction; Bacteria preservation
Introduction
Oenococcusoeni is a wine-associated lactic acid bacterium mostly responsible for wine malo-lactic fermentation (MLF) [1], which is introduced into starter cultures, is able to grow after alcoholic fermentation [2]. Its general trait is high tolerance to harsh wine environmental conditions: high ethanol concentration, low pH, poor proportion of nutrients, etc. [3]. Malo-lactic fermentation is necessary not only to deacidify some wines and to stabilize others, but also to improve the quality of wine apparently by addition of certain products of this metabolism, which make its flavormore complex [4]. In wine, many factors can cause a delay in MLF initiation, such aslow pH, low temperature, high ethanol, high SO2, but of these, the most important factor is the property of strain. These are the things that our team has been doing over the years. This paper introduces the advances of our team to review the work can be conducted on O.oeni.
Genetic Diversity
Because the important position in wine-making process, the screening and identification of O. oeni get more and more attention. 24 strains of O. oeni were isolated from different Chinese wines regions in 2000, and the isolation, culture and rapid identification system were also made [5-9]. In order to select the most active strains for malo-lactic fermentation, the strains’ abilities of resistance to wine condition (ex. low pH, high alcoholic concentration and SO2 content) were investigated. The results indicate that different strains have different adaptability in the performance of malo-lactic fermentation. In selected strains, O. oeniSD-2a was more active than commercial type strain O. oeni 31DH, and O. oeni SD-1b, O. oeni SD-2i and O. oeni SD-2h also showed strong abilities to survive in stress conditions [6]. And the wine inoculated with O. oeni SD-2a was stable and less volatile acid produced [10,11]. The quality comparison between the red wine inoculated by direct vat set (DVS) O. oeni SD-2a starterand commercial MLF starter (Viniflora® Oenos) were conducted both at laboratory and factory, and the O. oeni SD-2a starter achieved good results [12,13]. All these studies have laid a solid foundation for the further application of O. oeni SD-2a in wine making industry. The strain O. oeni SD-2a have obtained patent protection (02123444.2).
Differentiation of isolates was carried out by analysis of random amplified polymorphic (RAPD) pattern. The RAPD profiles (113 different binds) are strain specific and can divide strains into two main groups. And on this basis, we established single-enzyme amplified fragment length polymorphism (SE- AFLP) reaction system to study the genetic diversity of O. oeni [8,14]. The SE-AFLP bands generated by four selected primers can discriminate 22 strains of O. oeni [14]. SE-AFLP molecular marker can be used to differentiate O. oeni strains. Recently, 49 strains of malalactic bacteria were isolated and purified from Xinjiang wine, Hebei wine, Gansu wine after alcohol fermentation [15,16]. Among them, five strains have higher applicability in wine producing. These strains still need a further research.
The multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were also used to study the genetic polymorphism and evolutionary relationship of these isolates. The result showed that the MLST and PFGE method both separated the strains into two clusters which are correlated with the wine-producing regions. And the combination of results from both typing methods allowed a better discrimination of genotypes [17,18].
By now, the genome complete map of O. oeni SD-2ahas been constructed, it is the first genome complete map of O. oeni isolated from Chinese wine, and the second O. oeni strain with a genome complete map (unpublished). From the genome-wide comparison analysis, the size difference between O. oeni SD-2a and O. oeni PSU-1 is 209,186nt (SD-2a is 1,989,703nt, and PSU- 1 is 1,780,517nt), and the number of ORFs is 2071 and 1701, respectively. This indicated that substantial inter-strain genomic variation, in accordance with previous studies [19,20].
The adaptive stress response
Several studies have been made of how O. oeni responds under stress conditions [21]. Different mediums and initial culture pH differ in changing intracellular MLF activity, H+-ATPase activity [22]. Compared with FMATB and MATB, cells cultured in ATB increased inoculation viability and freeze-drying viability. And, ATB medium increased distinctly the relative concentration of lactobacilli acid (C19cyc11) and U/S ratio in cell membrane lipid composition of O. oeni SD-2a [22-24].
Malo-lactic enzyme gene (mleA) and malate permease gene (mleP) are two important genes of O. oeni involving in MLF. Malo- lactic enzyme is the function enzyme to turn L-malic acid into L- lactic acid during malolactic fermentation (MLF), while malate permease performs malic acid and lactic acid transport. The expression of mleA and mleP genes from O.oeni SD-2a and their co-expression have done in Saccharomyces cerevisiae. The coexpression of mleA and mleP gene in strain YSGA-GP results in a much higher MLF activity [25-27]. And many other stress related proteins and their genes are being discovered and reported.
Biological properties
In the process of our study, we found that O. oeni have antioxidant activity, which has great significance to its application in food and wine industry. The antioxidant properties and viabilities of 20 strains in simulated gastric and intestine juice and bile solution were measured and analyzed, to explore the probiotic effect of O. oeni strains, and assess the effects of these potentially probiotic bacteria. In addition, the possible anti-oxidative mechanism of O. oeni was elucidated. The results suggested that the anti-oxidative parameters were widely dispersed, irrespective of the evaluation methods used, which indicated that anti-oxidative properties depended on the strain and culture medium. The anti-oxidative mechanisms of O. oeni could be assigned to the 2,2- diphenyl- 1-picrylhydrazyl (DPPH) scavenging ability, reactive oxygen species (ROS) scavenging ability, iron ion chelation (FE), glutathione system, ferric reducing ability of plasma (FRAP), reduction activity (RA), inhibition of ascorbic oxidation (TAA), and linoleic acid oxidation (TLA) abilities [3,28]. Besides, the changes of amino acids were various in wine after malo-lactic fermentation by different O. oeni strains: the variety and concentration of amino acids had increased, some of them have particular biochemical and physiological properties, which can improve the nutritional value and sanitarian function [10].
The O. oeni strains could be potentially used as a novel probiotic strain in the food and wine industry, not just the starter of MLF. Thus, the deeper studies need to be performed in order to validate their potential use as probiotics or functional food additives [29]. Furthermore, O. oeni possessed a unique defense system to resist ROS, and the genes involved in the defense against oxidative stress need more attention.
Bacteria reconstruction and preservation
The research for construction of de-acidification wine yeast has been conducted by protoplast fusion with Saccharomyces ellisoideus1450 and O. oeni SD-2a. A single clone strain named F-20-7 with strong activity was selected. This strain can degrade L-malic acid during alcoholic fermentation. The alcohol fermentation capacity of F-20-7 approximates to S. ellisoideus 1450, and could degrade malic acid at the same time [30,31].
Due to the feature variation of microorganism is fast, so the preservation of microbial strains is critical. The cryopreservation protocol followed by the cultures of O. oeni have been studied, the storage of O. oeni in liquid nitrogen by using the composite protective agent (yeast extraction, glycerin, sugar and monosodium glutamate) prove to be well for strains preserved in culture collections [32 33].
Conclusion
As the most important executant of MLF, efforts should be made to select strains that are more suitable for conducting of MLF and reconstruct existing strains. The biological properties of wine after MLF should be properly explored and organized. And with the widely application of molecular biology technology in various fields, more and more technologies are applied to study the stress response of microorganisms, such as omics technology, gene knock-out technology, gene knock-in technology, gene silencing technology, etc. But, in the study of O. oeni stress response mechanisms, these technologies are still in the start stage. This needs a further study.
Funding
This work was supported by National Natural Science Foundation of China (Grant No. 31471708).
Acknowledgment
The authors would like to thank anonymous reviewers for their comments and suggestions which greatly improved the original version of the article.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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