96459 - General and Food Microbiology

Learning outcomes

At the end of the course, the student knows the structural, physiological and metabolic characteristics of the various microbial species. Furthermore, he knows the chemical, physical and biological factors that influence the development and survival of pathogenic, degradative and useful microorganisms of food interest. Finally, the student is able to identify and predict the effect of the formulation and technological processes, including fermentation ones, on the quality and safety of food.

Course contents

Bacterial classification. Phylogeny. Methods for classification: genotype and phenotype. Definition of the main genera and species of interest for food microbiology. Bacteria classification. Main Phyla (Proteobacteria, Firmicutes, Actinobacteria). Characteristics and location of the main bacterial microbial groups: Pseudomonadaceae, Enterobacteriaceae, Acetic bacteria, Acinetobacter and Chromobacterium, Vibrio and Photobacterium, lactic bacteria, Bacillus, Clostridia, Staphylococci, Micrococci, Listeria, Corineformes, propionic bacteria, bifidobacteria.

Classification of fungi: yeasts and molds. Sexual reproduction and asexual reproduction; ascomycetes and basidiomycetes.

Structure of the cell. Composition and general functions of the microbial cell. Morphology and structure of microbial cells. Eukaryotic cells and prokaryotic cells: differences and common characteristics. Spore formation

Cell growth. Culture media: definition, classification, preparation. Counting of microorganisms. Microbial growth curve: lag phase, exponential phase, stationary phase and death phase. Diauxic growth, chemostats. Concept of homeostasis. Main intrinsic and extrinsic factors influencing microbial growth

Nutrition and cellular transport systems. Chemical components. Energy (phototrophy, chemotrophy, lithotrophy). Organic substance (autotrophs, heterotrophs). Growth factors. Transport systems (primary, secondary, group translocation).

Microbial metabolism. Energy processes. Fermentation and breathing. Electron transport, redox potential and bioenergetics. Membrane transporters (NADH, quinones, citrocomas, Fe S proteins, flavoproteins). Proton Motive Force, ATP CoA. FPM generation: phases. ATPase

Energy cycles. Glycolysis. Entner Doudoroff. Oxidation of pentose phosphates. Fermentations: homolactic, heterolactic, alcoholic, mixed acid, butanediol, acetic, butyric. Aerobic and anaerobic respiration. Krebs cycle. Macromolecule catabolism

Viruses: viral structure, genetic material of viruses. Viral replication: Virulent and temperate phages. Characteristics of lysogenicity.

Role of pathogenic, useful and harmful microorganisms in food: microorganisms and food quality: impact of microorganisms on hygienic safety and sensory and nutritional quality of food. Impact of pathogenic and degradative microorganisms on food quality management. The growth of microorganisms: optimal conditions, stressful conditions. Kinetics of growth and death and types of factors that affect development / death. Microbial ecology applied to food.

Factors affecting the development and survival of microorganisms in food: Intrinsic factors: pH, water activity, redox potential, microstructure, nutrient antimicrobial compounds. Extrinsic factors: Temperature, humidity, gas composition in the headspace, microbial interactions. Surface contamination: Factors that determine adhesion and biofilm formation.

Control of microorganisms: Physical, physical and biological treatments: Use of temperatures, pressures, ionizing radiations, gas mixtures, synthetic and natural antimicrobial substances, protective microbial cultures. Combined treatments: Effect of combined technological treatments on the survival and development of microorganisms. Control of contamination, development and survival in food. Main microbial groups of food interest: Pseudomonadaceae, Acetic bacteria, Enterobacteriaceae (Coliforms, E.coli), Micrococcaceae, Lactic bacteria, Bifidobacteria, Propionic bacteria, Bacillaceae, Clostridia, Yeasts, Molds.

Risk factors in the food ecosystem: Influence of formulation, process and distribution on contamination, development and microbial survival, microflora associated with specific foods.

 

During the course, a laboratory training will also be carried out on:

• the use of the optical microscope to observe the morphology of the microbial cells of yeasts, bacteria and molds

• the techniques for the isolation, purification and conservation of food isolates

• staining techniques for the differentiation and highlighting of microbial cell components: Gram stain, spore and capsule staining

• physiological tests and enzymatic reactions for the characterization of the isolates: catalase, oxidase,

• tests to assess the needs of the isolates in terms of nutrition, of the relationship with oxygen and temperature

• the enumeration of cell cultures using direct and indirect methods: optical density, direct plate counting

• the evaluation of the development of cell cultures by means of seeding on plates by inclusion and by surface spatulation

• the analysis of experimental data: construction of growth curves and determination of the growth phases of cell cultures

 

Visits to companies, expositions, events etc,

 

 

Readings/Bibliography

• Brock. Biologia dei microrganismi. Microbiologia generale, ambientale e industriale. Pearson editore
• B. Ray 2003 Fundamental Food Microbiology CRC Press
• Giovanni Antonio Farris, Marco Gobbetti, Erasmo Neviani, Massimo Vincenzini Microbiologia dei prodotti alimentari (2012) Casa Editrice Ambrosiana ISBN: 978-88-08-18246 (ultima versione pubblicata)
• Luca Cocolin Marco Gobbetti Erasmo Neviani. Microbiologia alimentare applicata. Casa Editrice Ambrosiana. Distribuzione esclusiva Zanichelli; 2022.
• Slides and other scientific litterature provided during the course

Teaching methods

Lectures, seminars, educational visits to restaurant and catering companies and analysis of case studies

Assessment methods

Verification of learning takes place through an oral exam. The exam generally consists of three questions aimed at ascertaining the basic knowledge of microbiology, of the factors that influence microbial ecology and of their application in the main food ecosystems.

Teaching tools

Video projector, PC, slides, movies

Links to further information

https://www.researchgate.net/profile/Andrea_Gianotti ; https://www.linkedin.com/in/gianottiandrea/?originalSubdomain=it

Office hours

See the website of Andrea Gianotti

See the website of Lorenzo Nissen