Over the last 20 years wine-making technology has seen remarkable developments, which have improved the quality of the wines produced and have also made it possible to prepare wines with a range of characteristics. In this field, some biotechnological techniques have been of fundamental importance. Among these technological innovations, enzymic treatments, selected yeasts, improvement of microbial starters, and microorganism immobilization are reviewed here. A concise report is presented on the possibilities offered by enzymes that catalyze the transformation of polysaccharides, proteins, and polyphenols. We illustrate the importance of the characteristics of wine yeast and of a genetic improvement program for the wine industry, as well as the complexity of the genetic modifications of commercial wine yeast strains. We summarize the research on the optimization of new processes such as the use of immobilized microorganisms and cell-recycle batch fermentation in the preparation of wines and sparkling wines.

Recent Applications of Biotechnology in Wine Production

Malolactic fermentation conducted by lactic acid bacteria follows alcoholic fermentation during winemaking, and several positive effects make it indispensable for most wines. Research has focused on the growth and physiology of lactic acid bacteria in wine; resulting in the design of malolactic starter cultures. Future work on these starters will concentrate on aromatic changes as additional criteria for strain selection. Although the main features of the malolactic enzyme and its gene are known, the detailed mechanism of the malolactic reaction remains unclear. Cloning and expression of this activity in enological strains of Saccharomyces cereuisiae might be one of the next most important advances in the control of malic acid degradation in wine.

Microbiology of the malolactic fermentation: Molecular aspects

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2893%2980488-G

Cloning, sequence and expression of the gene encoding the malolactic enzyme from Lactococcus lactis.

Growth of the malolactic bacterium Leuconostoc oenos was improved with respect to both the specific growth rate and the biomass yield during the fermentation of glucose-malate mixtures as compared with those in media lacking malate. Such a finding indicates that the malolactic reaction contributed to the energy budget of the bacterium, suggesting that growth is energy limited in the absence of malate. An energetic yield (YATP) of 9.5 g of biomass.mol ATP-1 was found during growth on glucose with an ATP production by substrate-level phosphorylation of 1.2 mol of ATP.mol of glucose-1. During the period of mixed-substrate catabolism, an apparent YATP of 17.7 was observed, indicating a mixotrophy-associated ATP production of 2.2 mol of ATP.mol of glucose-1, or more correctly an energy gain of 0.28 mol of ATP.mol of malate-1, representing proton translocation flux from the cytoplasm to the exterior of 0.56 or 0.84 H+.mol of malate-1(depending on the H+/ATP stoichiometry). The growth-stimulating effect of malate was attributed to chemiosmotic transport mechanisms rather than proton consumption by the malolactic enzyme. Lactate efflux was by electroneutral lactate -/H+ symport having a constant stoichiometry, while malate uptake was predominantly by a malate -/H+ symport, though a low-affinity malate- uniport was also implicated. The measured electrical component (delta psi) of the proton motive force was altered, passing from -30 to -60 mV because of this translocation of dissociated organic acids when malolactic fermentation occurred.

Electrogenic malate uptake and improved growth energetics of the malolactic bacterium Leuconostoc oenos grown on glucose-malate mixtures.

Summary The use of Oenococcus oeni starter cultures for the induction of malolactic fermentation (MLF) in wine permits control over the timing of the process and the quality of the wine. Successful inoculation of bacterial starter cultures into wine depends on the selection of suitable strains and on the preparation and conservation of those cultures. Medium for Leuconostoc oenos (MLO) is the best medium for easy and rapid growth of O. oeni cultures under laboratory controlled conditions for isolation and identification. However, this study showed that O. oeni cells inoculated in MLO failed to induce MLF in wine while cells grown in Medium of Preculture (MP) or wine, stored at −20 °C or freeze-dried retained the ability to induce MLF when inoculated in wine. Our results suggest that the use of freeze-dried cultures of O. oeni previously grown in MP is the best choice for industrial application.

/pdf/the-effects-of-freezing-and-freeze-drying-of-oenococcus-oeni-3hqqfgevnf.pdf

The effects of freezing and freeze-drying of Oenococcus oeni upon induction of malolactic fermentation in red wine

Optimization of the conditions for preparing bacterial cultures for malolactic bioconversion

The malolactic enzyme of Lactobacillus sp. 89 was purified 142-fold from 1.51 mmol/min/mg to a specific activity of 214 mmol/min/mg of protein. The molecular weight determined by gel filtration was 120.000. The enzyme consists of two identical subunits (M r 60,000) identified after treatment with sodium dodecyl sulfate. Malolactic enzyme is the only enzymatic system which catalyzes the NAD- and Mn 2+ -dependent transformation of L-malic acid into L-lactic acid and CO 2 in Lactobacillus sp. 89

Purification and properties of a malolactic enzyme from a Lactobacillus sp. able to perform the malolactic fermentation of wines

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Optimization of the conditions for preparing bacterial cultures for malolactic bioconversion

Purification and properties of a malolactic enzyme from a Lactobacillus sp. able to perform the malolactic fermentation of wines