04221 - Industrial Microbiology

Learning outcomes

The principal aim of this course is to give the students information on the main microbial groups involved in industrial processes, i.e. the microorganisms responsible for fermentations of industrial relevance. Hence, students will be given all the information necessary to manage, optimize and control microbial metabolic activities in biotechnological processes aimed at biotransformation of substrates and raw food materials into microbial metabolites and fermented foods thus preventing food diseases.

Course contents

Introduction to the course: presentation of the teacher, overview on the aims of the course, the topics addressed, the recommended textbooks, how teaching material is provided to students and how the final examination is carried out.

The topics of the course include both a general part and one related to some of the main products of industrial microbiology. Also practical lab activities will be performed.

General part

1. A brief introduction to industrial microbiology - brief history, information on microrganisms, industrial and food fermentations.

2. Microrganisms of industrial relevance

- Retrieve the main microorganisms of industrial interest and their metabolic activities: lactic acid bacteria, probiotic microorganisms, acetic acid bacteria, microstaphilococi, yeasts, molds

-Industrial collections of microorganisms, and techniques for their preservation: liquid, frozen, freeze-dried cultures.

- Traditional techniques of selection and improvement of micro-organisms of industrial interest: primary and secondary screening, mutagenesis, final selection.

3. Microbial metabolites

- Primary and secondary metabolìtes: types, characteristics and kinetics of production.

- Control and regulation of microbial metabolism: mechanisms of inhibition and repression by feed-back of linear and branched metabolic pathways.

- Techniques for the accumulation of microbial metabolites: modulation of the composition of the fermentation substrate; changes in cell membrane permeability; metabolic block; removal of inhibition/repression mechanisms.

4. Biotecnology of fermentations

- Substrates for industrial fermentations: the main ingredients used as carbon sources (e.g. molasses, whey, spent sulphite liquor, agricultural wastes, starch,..) and nitrogen sources (e.g. vegetable flours, corn steep water, yeast extract, peptone,..) , vitamins and growth factors, oils, fats, anti-foam and surfactants.

- Main criteria for the classification and differentiation of industrial fermentations: type of products, kinetics of production, methods of cultivation and fermentation technology.

- Types of fermentations: type I, II and III. Dynamics of microbial growth and production of metabolites.

- Technology of microbial cultivation: solid state fermentation, superficial or submerged fermentations. Main characteristics, pro and cons, examples of use.

- Fermentation Technology: batch, fed-batch, continuous fermentations. Main features, critical aspects and benefits.

- Mathematical modelling of microbial growth, metabolites production and substrate consumption.

- Industrial fermenters: main features and control parameters. Classification of bioreactors according to the aeration and agitation systems. Main characteristics of the fermenters with a mechanical stirring (stirred tank reactor), pneumatic stirring (air lift, bubble column), hydraulic stirring, packed or fluid bed reactors.

- Sterilization of fermenters and substrates. Simultaneous or separate sterilization. Continuous or batch processes. effectiveness of sterilization calculation.

5. Immobilization techniques - Procedures for passive immobilization (aggregation, adsorption and colonization) and active immobilization (covalent bonds with the matrix, cross-linking, microencapsulation) of enzymes or mmicrobial cells. Advantages and disadvantages of immobilization. Fermenters for immobilized microbial cells. Examples of industrial application of immobilized mirobial cells/enzymes.

 

Main products in industrial microbiology

1. Fermented foods - Main characteristics, natural/spontaneous or guided fermentations. Microbial starter cultures: definition, classification, role and criteria for their selection.

2. Dairy products: yoghurt, fermented milks and cheeses. Definitions, types and main characteristics. Role of the various starters and natural microflora in the biochemical changes that characterize fermentation and/or ripening.

3. Bakery products - direct and indirect bakery technology. Types of biological leavening agents - bakery yeast and sourdough - and their role in breadmaking. Sourdoughs: type I , II and III ; main features, dominant microflora and their effects on the characteristics of leavened baked products.

4. Fermented cured meats: definition, characteristics and classification. Evolution of the microbial population in relation to the characteristics of the matrix and to the phases of the production process. Role of starters in primary fermentation. Biochemical changes during the ripening phase.

5. Microbial biomasses -  Bakery yeast, starter and non starter microbial cultures: main characteristics in relation to their use. Yeasts for bakery industry: metabolic aspects, substrate and conditions of fermentation, recovery andstorage conditions.

6. Exopolysaccharides (EPS). General characteristics and classification criteria, mechanism of biosynthesis and factors affecting the production kinetics. Examples of use of some microbial EPS.

Practical activities

Classroom exercises on modeling of microbial growth, production of metabolites or microbial biomass in relation to the type of fermenter.

Laboratory work related to the: (i) primary screening of microorganisms of industrial interest; ii) recovery and growth of microbial starters; iii) the choice of microbial starters for food fermentation in relation to their technological features; iv) the effect of different raw carbon sources on the growth of starter cultures; v) enzymatic activities (proteases and lipases) of food-related microorganisms; vi) Production of exopolysaccharides.

 

Readings/Bibliography

- Manzoni Matilde "MICROBIOLOGIA INDUSTRIALE", Casa Editrice Ambrosiana
- Farris G.A., Gobbetti M., Neviani E., Vincenzini M. "MICROBIOLOGIA DEI PRODOTTI ALIMENTARI", Casa Editrice Ambrosiana
- Lecture notes provided by the teacher through AMS Campus - AlmaDL - Università di Bologna.
- Papers on specific topics suggested by the teacher

Teaching methods

Class lectures, laboratory practises, seminaries held by food sector experts, guided tours to food production plants.

Assessment methods

The final evaluation will be based on a written test and an oral presentation.
As far as the written test, nNo lecture notes, books, PC, internet connection is allowed during the text. The maximum time available for the test is 150 minutes. The test consists of 4 open questions and 26 question some of which based on multiple choiche questions, mute figure, exercises, definitions.... Overall the written text aims at the evaluation of the knowledge of the topics taught during the class lecturs. Also the ability to solve some of the problems faced during practise exercises and laboratory activities will be evaluated. The score of the open questions corresponds to a maximum of 2 points for each of them, while that of the 26 questions is different according to type of exercise, but it will still be clearly reported in the text close to each question. The test is passed provided that a score of at least 18 points is reached.

The oral talk will be given through a power point presentation on a topic chosen by students in agreement with the teacher. Such a presentation will be aimed at describing an industrial process, a fermented food or compouds produced through a microbial fermentation also highlighting the most critical aspects.

The final mark of the course unit of "Industrial Microbiology" will be based both on the evaluation of the written test (90%) and the oral presentation (10%).

The final evaluation of the course of "Food Microbiology" will be the arithmetic mean of the marks of the two course units "Food Microbiology" and "Industrial Microbiology".

Teaching tools

Slides of the lectures and training activities in the laboratory of food microbiology will be availablr for students as pdf files through the web-site: https://campus.unibo.it/

Username and passord to login and download educational material will be given to students enrolled at the University of Bologna by the professor during the first lesson.

Office hours

See the website of Lucia Vannini