The course will introduce general principles on the structure, physiology, biochemistry, genetic, and ecology of microorganisms with the ultimate goal to understand their growth and survival strategies, and to avoid uncontrolled microbial proliferation. Basic microbiological techniques will be presented, as well as the most advanced methods for the characterization of microorganisms.
The course will provide the instruments needed to acquire theoretical and practical skill on the biotechnological aspects of fermentation and transformation of must and wine, and on the stability of the final product. These skills are of great importance to understand, manage, and optimize the activities of yeasts and bacteria in relation to the characteristics of the must and the wine to be obtained, as well as of the productive process applied.
Laboratory exercises are designed to acquire manual ability in the application of classical and innovative microbiological methods.
Part I. Agricultural microbiology.
Historical development of microbiology. The cell: general concepts, the distinction between prokaryotes and eukaryotes. Morphology and cytology of the microbial cell. Structures and functions of prokaryotic cell: cell wall, capsule, flagella, cytoplasmic membrane, cytoplasm, organelles, ribosomes, reserve materials, bacterial genome. The bacterial spore.
Microbial nutrition. Cultural techniques, techniques of selection and isolation. The micro-organisms and the environment: responses to temperature change, oxygen tension, pH, and water activity. Kinetics of microbial growth. Control of microorganisms by physical and chemical agents.
The microbial metabolism. The aerobic and anaerobic respiration. The main fermentations.
Overview of microbial genetics. The genetic information in bacteria: bacterial chromosome, plasmids and transposons. Mutations: selection and identification of mutants. Horizontal transfer of genetic information between bacteria: transformation, conjugation, and transduction. Production of recombinant bacteria. Viruses. The bacteriophages: lytic cycle and lysogeny.
Classification of microorganisms. The concept of species. Classical and molecular taxonomy. Groups of microorganisms.
Part II. Wine Microbiology.
The microorganisms of oenological interest: yeasts and bacteria in winemaking. The yeasts: classification, metabolism, reproduction, genetics. The must as a substrate for microbial development. The alcoholic and malolactic fermentations. The principal and secondary products of fermentation. The lactic acid bacteria: definition and classification. The malolactic fermentation: effects on the sensory characteristics and the wholesomeness of wines. Other microorganisms of oenological interest: acetic acid bacteria and mould. Wine spoilage of microbial origin. Definition and characteristics of spoilage microorganisms. Production of biogenic amines, etilcarbammate and ochratoxin.
Microbial ecology: the spontaneous fermentation of grape must. The controlled fermentations. Starter cultures of yeasts and malolactic bacteria for wine. Clonal selection of yeasts, genetic improvement, selection of technological and qualitative characteristics, autolytic capacity. Clonal selection of malolactic bacteria, selection of technological and qualitative characteristics. Use of microbial inoculants in oenology. Working conditions, induction / arrest of alcoholic fermentation. Microbial interactions and wine quality. Methods for the isolation, identification and technological characterization of yeasts and malolactic bacteria. Traditional methods. Direct and indirect rapid methods. Molecular techniques.
Part I. Agricultural Microbiology.
The microbiology laboratory: tools and equipments. Introduction to the basic microbiological techniques (culture media preparation, sterilization techniques, pure culture method, serial dilutions).
Research of specific microbial groups in samples of different origin.
Plate counts. Spread plate.
Observation at the optical microscopy of wet samples.
Simple and differential staining of microorganisms.
Identification of microorganisms through miniaturized systems.
Part II. Wine Microbiology.
Microscopy observations of the microorganisms of oenological interest (elliptical and apiculate yeasts, lactic acid bacteria, acetic bacteria, moulds).
Analysis of the microbiological quality of yeast starter cultures. Isolation of yeasts.
Technological and physiological tests on yeast isolates.
Extraction of DNA, and genetic typing of Saccharomyces cerevisiae.
Microvinification tests and monitoring of fermentations.