At each stage of winemaking, the winemaker is not alone – he coexists with invisible "colleagues": microorganisms. Every winemaker must be familiar with the microorganisms that act in his must and then in his wine, and to distinguish those that can be beneficial or, on the contrary, harmful. In recent years, genetic analysis methods have significantly advanced the microbiology of wine. Malolactic fermentation and lactic acid bacteria in wine have been fully affected by this development of scientific knowledge. Malolactic fermentation is a relatively recent step in the wine-making process, but of considerable importance. All the work carried out upstream (quality of the grapes, alcoholic fermentation) and downstream (ageing, stabilisation and preparation of the wine for packaging) can be affected by its progress. However, malolactic fermentation is often a haphazard and insufficiently ma stage of winemaking. This book is the first synthesis work that addresses both the fundamental scientific bases on lactic acid bacteria in wine and the malolactic fermentation process, recent developments in research (in its first part) and situations encountered in production, through numerous experiments and field observations (in its second part). Illustrated with many specific examples and detailed protocols, this book is intended for all wine practitioners and professionals. Nologists, producers, laboratories and students of nology will find a lot of technical information allowing them to better understand the complexity of malolactic fermentation, to optimize its progress in their cellar as well as the appropriate tools to solve certain specific problem situations. Researchers will find practical applications of their work and possible ways of improving in order to better respond to the problems encountered by practitioners in the field on a daily basis. Vincent Renouf carried out his doctoral work on the study of the oenological microbial system, then devoted himself to the study of malolactic fermentation as head of R&D within the Laffort group in close collaboration with scientists and oenologists, in France and abroad. Between 2010 and 2013, he held the position of Technical Director. He co-authored Wine Microbiology - Fundamental Bases and Applications and is also the author of some sixty scientific and technical publications on wine microbiology and malolactic fermentation.