1、 Chapter 2 Preparation of Culture Medium Unit 1 Industrial Fermentation Medium The basic ingredients of media include carbon source、nitrogen source、inorganic salt、growth factor and distilled water etc.Medium DevelopmentnTo maintain economic competitiveness,low-cost crude materials are frequently use
2、dnLevels of minerals and growth factors may be criticalKinds of Culture Media The source of media constituent Complex mediaSynthetic or defined mediaSemi-defined mediumPhysics statesLiquid mediumSolid mediumSemi-solid mediumFor useBasic mediumEnriched mediumDifferential mediumSelective mediumManufac
3、ture intentionSeed mediumFerment mediumNutrient sources for industrial fermentationCarbon&energy source+nitrogen source+O2+other requirements Biomass+Product+byproducts+CO2+H2O+heatNutrientRaw materialCarbonmolasses,starchNitrogencorn steep liquor,soybean meal,pure ammonia or ammonium salts,urea,nit
4、rate salts,phosphate saltsVitamins and growth factorsbiotin,yeast extract,beef extract,corn steep liquor,wheat germ mealFermentation media1.Carbon sources (1)Starch(corn,wheat,potato)Widely used in fermentation industryStarch dextrin glucose Advantages:cheaper than glucose(2)MolassesByproduct of can
5、e or beet sugar productionA dark viscous syrup containing 50%-75%fermentable sugars(mainly sucrose)with 2%nitrogen,vitamins and mineralsCheaper 2.Nitrogen source (1)Inorganic nitrogen source Ammonia,ammonium and nitrate Microbes can utilize it faster.After it is utilized,the pH of medium will be cha
6、nged.(NH4)2SO4 2NH3+H2SO4 NaNO3+4H2 NH3+2H2O+NaOH(2)(2)Organic nitrogen sourcesUreaYeast extractPeptonesCorn steep liquorSoybean cake powder Peanut powderBran hydrolysis liquidcorn steep liquor powder3.Trace elements Fe,Mn,B,Zn,Cl,Mo,Cu4.Growth factors Small amount of organic compounds necessary for
7、 microbial growth.e.g.amino acids,vitamins,biotin Sources:normally organic nitrogen source e.g.corn steep liquor Corn steep Liquor,CSLnCorn steep liquor is the water extract by-product resulting from the steeping of corn during the commercial production of corn starch and other corn products.Differe
8、nt medium for different food products Chinese distilled spirit：solid medium Fruit spirit：fruit juice or fruit sauce Beer：wort Alcohol:starch mash Amino acid:starch mash Citric acid：starch mash Lactic acid：starch mash Unit 2 Preparation of Starch Sugar Starch is a large molecule that is made of branc
9、hing chains of glucose molecules.It can be broken down into glucose by hydrolysis.nStarch found in grains,potatoes,beans,peas,cassava nTypically 20-30%amylose,remainder amylopectinCharacteristics of starchInsoluble in hot waterBlue complex compound by reaction with iodine.Insoluble in 30%of ethanol
10、solution or above.Hydrolyzed by acid and enzyme,the ultimate product is glucose.starch granuleIV.A.ii.-20Starch:AmylosenAmylose is a linear glucan with 1,4 glycosidic linkagesO OO OH HC CH H2 2O OH HO OH HO OH HO OO OH HC CH H2 2O OH HO OH HO OO OO OO OH HC CH H2 2O OH HO OH HO OO OH HC CH H2 2O OH
11、HO OH HO O.O OH H 1 1,4 4 l li in nk ka ag ge eL Li in ne ea ar rr re ed du uc ci in ng g e en nd d-D D-g gl lu uc co os se eIV.A.ii.-21Starch:AmylopectinnAmylopectin is a branched glucan with 1,4 and 1,6 glycosidic linkagesO OO OH HC CH H2 2O OH HO OH HO OO OO OH HC CH H2 2O OH HO OH HO OO OH HC CH
12、 H2 2O OH HO OH HO O.B Br ra an nc ch he ed d.O OO OH HC CH H2 2O OH HO OH H.O OH HO OO OH HO OH H.O OC CH H2 2O O 1 1,6 6 l li in nk ka ag ge er re ed du uc ci in ng g e en nd d 1 1,4 4 l li in nk ka ag ge e-D D-g gl lu uc co os se eStarch:Amylopectinnless extended(more compact)than amylosenlarger
13、MW 1,6 linkages 1,6 branch points result in tree-like structurer re ed du uc ci in ng g e en nd dWhy should starch be hydrolyzed to glucose?1.Most microbes could not utilize starch directly.2.To obtain sugar from the starch of many different plants,rather than just sugar beets or sugar cane.Conversi
14、on of starch to fermentable sugars 1.Acid hydrolysis method Starch slurry is acidified to a pH value and then heated in a converter under pressure.(C(C6 6H H1010O O5 5)n n (C(C6 6H H1010O O5 5)x x C C1212H H2222O O11 11 CC6 6H H1212O O6 6 amylum dextrin oligosaccharidesglucoseDue to heat and acid,th
15、ere are Glucose combination reaction combination reaction and and decomposition reactiondecomposition reaction starch glucose oligosaccharide colour content(difficult to utilize)(difficult to decolor)Total lost of glucose 7 7 1shortening the starch(Liquefaction)glucoamylase-produces glucose(sacchari
16、fication)glucose isomerase-convert to fructose(isomerization)3.Acid-enzyme combination method (Two-stage hydrolysis)Slurry is only partially converted by acid and then treated with an appropriate enzyme or enzymes until the conversion is complete.1)Acid-enzyme hydrolysis Acid-liquefaction Glucoamyla
17、se-saccharificationSuitable for:starch granule is hard2)Enzyme-acid hydrolysis-Amylase(thermostable)-liquefaction Acid-saccharificationSuitable for:starch granule size is irregular Production of Glucose from StarchItemsItemsacidacidacid/enzymeacid/enzymeenzymeenzymeDEDE valuevalue919195959898ColorCo
18、lor10100.30.30.20.2Processing condition HTPHTPNTPEnergy consumingEnergy consuminghighhighhighhighlowlowBy-productBy-productmoremoremoderatemoderatelittlelittleCycle time Cycle time shortshortmoderatemoderatelonglongReview Questions1.Which kind of carbon source and nitrogen source usually used in ind
19、ustry?Cite the advantages and disadvantages of the different choices.2.What is the definition of growth factor and its main source?3.What is the significance of getting sugar by hydrolyzing starch?4.Compare the three methods to produce glucose from starch and the difference between combination react
20、ion and decomposition reaction,liquefaction and saccharification.InductionRepression1.It turns the operon on.1.It turns the operon off.2.It starts transcription and translation.2.It stops transcription and translation.3.It is caused by a new substance,which needs enzymes to get used.3.It is caused b
21、y an excess of existing metabolite.4.It operates in a catabolic pathway.4.It operates in an anabolic pathway.5.Repressor is prevented by the inducer from joining the operator gene.5.Repressor is enabled by a co-repressor to join the operator gene.Feedback repressionFeedback inhibitionRegulation levelgenetic:RNA transcriptioncellular:activity of enzymeComplex formedend product+repressorend product+enzymeEffectoperator on DNA template occupied by the complexreduced enzyme activityConsequenceblocked transcription The respective reaction is inhibited.
