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Chapter 1 Strain Breeding Food microorganismsFood production microorganisms Produce new types of food Food spoilage microorganisms Cause spoilage of food and/or diseases3Use of MicroorganismsnPositivenProductionnConversionnNegativenPathogensnSpoilageFive Common Characteristics of Microorganisms1.Small volume,large surface area2.Fast absorption and conversion3.Rapid duplication and growth4.Strong adaptability5.Widespread distribution and diversified speciesWhat types of microorganisms cause fermentation to occur?nBacterianYeastnMold Bacteria Bacteria are typically one-celled organisms that multiply by simple division and can be seen only with a microscope.1.Lactic acid bacteriaLactobacillusyogurtStreptococcusyogurtPediococcussour picklesBifidobacteriumprobioticsLactobacillusStreptococcusPediococcusBifidobacterium2.Acetic acid bacteria Acetobactervinegar3.Glutamic acid fermentative bacteriumnCorynebacteriumglutamicumn nBrevibacteriumflavum Yeast Yeasts are unicellular(single-celled)fungi in which little or no mycelium develops and that ordinarily reproduce by budding.Happy YeastSaccharomyces cerevisiae 1.Saccharomyces Saccharomycescerevisiaebeer Saccharomycesellipsoideuswine 2.Candida CandidautilisSCPAbout SCP,which is correct?A.Is a kind of protein which extracted from microbial cells.B.Is microbial cell which produced by fermentation.C.Is antibiotics secreted by microbial cells.D.Could not be regarded as food.Mold(mould)Fungi that grow in the form of multicellular filaments,called hyphae.In contrast,microscopic fungi that grow as single cells are called yeasts.1.MucroChinese cheeseChinese cheese2.Rhizopus amylase3.Aspergillus A.nigercitric acid,glucoamylase A.oryzaesoy sauce,soy sauce,pasta(sweet)saucespasta(sweet)sauces4.Monascus pigment Choosing Microorganismsfor Industrial Microbiology genetically stable easy to maintain and grow well suited for extraction or separationof desire productStrain SelectionPurchase from Culture CollectionsScreening of nature circumstances MutationsCell biology techniquesGenetic engineering International Culture CollectionsAbbreviationNameLocationATCCAmerican Type Culture CollectionUnited StatesIAM Institute of Applied MicrobiologyUniversity of Tokyo,JapanNCTCNational Collection of Type CulturesLondon,United kingdomChina Culture CollectionsCGMCCChina General Microbiological Culture Collection CenterBeijingCulture CollectionsScreening of nature circumstances Most major sources of microbes for use in industrial microbiology are natural materialsMicrobial strain collection 1.soil slurry 2.Enrichment Special media Control condition Inhibit unwanted strain3.Isolation cultivation Streak plate method Pour plate method Spread plate method Streak plate method nBacteria are“streaked”over the surface of an agar plate so as to obtain single colonies.nIt can also highlight the presence of contaminating micro-organisms.This is an example of a good streak for isolation using the four corners method.Performing a Plate Streak IPerforming a Plate Streak IIPour plate method Bacteria are mixed with melted agar.Poured into an empty plate and allowed to solidify.Spread plate method Small samples of the diluted bacteria are pipetted onto the surface of agar plates.A sterile,bent-glass rod is then used to spread the bacteria evenly over the entire agar surface.Performing the Spread Plate method I100Performing the Spread Plate method II70%EtOHKeep flame away from alcohol!4.Pure cultivationGrow only one kind of microbeMust use aseptic technique to avoid contaminating the cultureTransfer a single colony from agar plate to liquid medium5.Productivity measurement Primary screening：quantity Secondary screening：qualityIf I couldnt find an ideal strain from nature,how would I do?qSpontaneous(natural)mutationqInduced mutationmutationTechnique for inducing mutationPhysical mutagens e.g.X-rays,g g-rays,UVChemical mutagens e.g.base analogs,nitrous acid,alkylating agents How are mutants detected by scientists?nVisiblenNutritional(auxotrophic)nWhat is replica plating,and how is it used to detect auxotrophic mutants?nResistance mutations(plate on media containing the chemical)Replica-plating technique to screen for mutant strains of a colony-forming microorganism.Q:How would you select for L-tryptophan-producing mutant strain?Cell Biology TechniquesnProtoplastnRemoving the cell wall with lytic enzymes in the presence of osmotic stabilizers.nIn the presence of fusogenic agent such as polyethylene glycol(PEG),protoplasts are induced to fuse and form transient hybrids or diploids.nRegeneration of viable cells from the fused protoplasts.Genetic EngineeringVarious high value added products have been produced fromgenetic engineeringmethods.Inoculum Development The preparation of a population of microorganisms from a dormant stock culture to an active state of growth that is suitable for inoculation in the final production stage.If fermentation in a large tank receive only one loop of inoculum,a prolonged period would result.energy consumingcontamination Necessity of inoculum development So the inoculum volume has to be quite largeA seed fermenter is usually required to produce the inoculum volumeThe seed fermenters purpose is not to produce product but to prepare inoculumIn inoculum developmentInoculum level:approximately 0.5 to 5 percent inoculum by volume from the preceding step.Incubation period:short,in log growth phase,little fermentation productInoculum media:balanced for rapid cell growth and not for product formation.The process of inoculum developmentInoculation of a fermenter from another seed tankSeedTankFermenterA BTrap TrapSteamCJDIHEFGIndustrial Fermentation Setting Review Questions1.Cite some micro-organisms used widely in food industry and their corresponding products.2.How to get an ideal strain for fermentation industry?3.Whats the purpose of inoculum development?Cite the process of it.4.Why can not the micro-organisms product excessive metabolites spontaneously?By which methods can we get the excessive metabolites?5.How to reduce the concentration of end products in fermentation?6.How to improve the permeability of cell membrane?
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