Microbiology & Biotechnology PDF

Microbiology & Biotechnology  Objectives Upon completion of this unit you should be able to: define biotechnology explain the role of biotechnology in the food industry describe the steps involved in the industrial production of alcohol, beer, wine, yogurt...

Microbiology & Biotechnology  Objectives Upon completion of this unit you should be able to: define biotechnology explain the role of biotechnology in the food industry describe the steps involved in the industrial production of alcohol, beer, wine, yogurt, cheese and bread making distinguish between homogenised and pasteurised list uses of biotechnology in fuel production  Microbiology: Branch of science that deals with microorganisms. Biotechnology: Exploitation of biological processes for industrial and other purposes, especially the genetic manipulation of microorganisms for the production of antibiotics, hormones, etc. Biotechnology is a field of applied biology that involves the use of living organisms and bio-processes in engineering, technology, medicine and other fields requiring bio-products Its major uses are in the production or preservation of food.  Traditional biotechnology For many centuries the process of fermentation has used micro-organisms (yeasts and bacteria) to make beer, yogurt ,cheese, bread making and pickling. The basis of the fermentation process is the conversion of glucose (sugar) to alcohol or to lactic acid and carbon dioxide by enzymes in the micro-organisms.  Uses of fermentation Preservation, converting a perishable food into one that has a longer shelf-life. Change the nutritional value of food products, e.g. converting milk to cheese. Improve sensory characteristics of foods (flavour, aroma and texture). FERMENTED BEVERAGE  Types of fermented beverage Alcoholic beverages are divided into three general classes: 1. Beers 2. Wines 3. Spirits  Beer making Ingredients Malted barley Hops Yeast Water  Cont’ ❖Barley -- a grain and the base ingredient of beer. ❖Hops--the ripe, dried blossoms of a perennial vine, in the mulberry family. Hops add a bitter flavor, pleasant aroma to beer and help to preserve it.  Cont’ ❖Yeast -- an important ingredient of the beer. This is a single celled fungus that plays the central role in converting sugars into carbon dioxide and alcohol during fermentation. Two main varieties of yeast. Saccharomyces cerevisiae. Saccharomyces carlsbergensis. ❖ Water-- beer is atleast ninety percent water, special consideration is given to how the water tastes before it goes into the brew kettle  Steps in beer making 1. Malting 2. Mashing 3. Fermentation 4. Sedimentation 5. Aging  1. Malting Barley is allowed to soak in water for about 2 – 3 days. Once the barley grains reach 40-45% moisture the barely is allowed to germinate. Germination of the grain allows for plant enzymes to convert starch into more simple sugars like amylases. Once the epicotyl forms, the grains are dried.  2. Mashing Dried barley has to be cracked open so that water can get inside and activate the enzymes. It is mixed with water (65oC). They convert the amylase from the barley into simple sugars maltose. This process is known as mashing.(starch to maltose and glucose) After the solids are strained out the dark, sweet liquid is called "wort“ The wort must be boiled for 30-90 minutes depending on the recipe.  Cont’ Hops are added at different times during the boiling phase. Hops contributing to the bitterness of the beer are added early in the boil so the resins have time to dissolve into the wort. Hops that are added for their aromatic flavoring are added within the last few minutes of the boil. Otherwise the quickly dissolved oils get steamed out of the wort.  3. Fermentation The wort is cooled, so the yeasts to be added next don't die. The yeast is allowed to ferment the wort for up to 5-14 days, depending on the type of beer. During this phase, the alcohol is made and the carbonation is allowed to escape through the fermentation lock.  4. Sedimentation After this, the dead yeast, proteins and hop resins are allowed to settle out, helped by ‘clarification agents’.  5. Aging The bottles are then set aside in a cool, dark place and left untouched until ready to drink. "Green beer" can be drunk at one week after bottling. Most home-brewers leave their beer sit three or four weeks before the first bottle is opened.  Yeast Ale yeast-favor higher temperatures between 17 - 22˚C, usually top fermenting with a greater O2 requirement. This is usually Saccharomyces cerevisiae. Lager yeasts-favor lower temperatures 1.6-10˚C, usually bottom fermenting, with a lesser O2 requirement. This is usually Saccharomyces uvarum (formerly known as Saccharomyces carlsbergensis).  Cont’ Yeast is added to the wort. The commonly used species of yeast are Saccharomyces cerevisiae and S. carlsbergensis. Enzymes in the yeast convert maltose to glucose. In the early stages of fermentation, yeast respires aerobically, oxidized the glucose to carbon dioxide and water and dividing rapidly. As the oxygen supply diminishes, anaerobic respiration takes over and the glucose is oxidized only as far as alcohol and carbon dioxide  Cont’ Respiration--the yeast converts simple sugars to carbon dioxide and water. The yeast obtains it's energy for fermentation and sedimentation during this phase. Fermentation--the conversion of sugar to alcohol and carbon dioxide. It is the longest of the three phases. Sedimentation--the yeast cells settle to the bottom of the fermentation vessel because most of the sugars have been converted and utilized for respiration, and then begin to prepare for dormancy. Sedimentation last for 2-3 days. At the time the beer appears clear, the yeast's density is less than 1 million cells per milliliter. Process of Beer Production  Wine Produced from the fermentation of fruit juice, usually from grapes. For white wines, white grapes are usually used, and the skins are removed from the must (“pressing”) before fermentation For red wines, red or black grapes are used, and the skin is allowed to remain during fermentation For rosé wines, red grapes are used and the juice is allowed to remain in contact with the skins just long enough for a rose or pink colour to develop  Processing Lines There are five basic components or steps to making wine: 1. Harvesting 2. Crushing and Pressing 3. Fermentation 4. Clarification (sedimentation) 5. Aging and Bottling  1. The Harvest Harvesting or picking is certainly the first step in the actual wine making process. In order to make fine wine, grapes must be harvested at the precise time, preferably when physiologically ripe. Harvesting can be done mechanically or by hand. Once the grapes arrive at the winery, reputable winemakers will sort the grape bunches, culling out rotten or under ripe fruit before crushing.  2. Crushing and Pressing Crushing the whole clusters of fresh ripe grapes is traditionally the next step in the wine making process. Today, mechanical crushers perform the time-honored tradition of stomping the grapes into what is commonly referred to as “must”. Mechanical pressing has also improved the quality and longevity of wine, while reducing the winemaker's need for preservatives. Up until crushing and pressing the steps for making white wine and red wine are essentially the same.  Cont’ The extracted juice is treated with sulphur dioxide to kill bacteria and naturally occurring yeasts. The sugar content and pH are adjusted before adding a starter culture of yeast, usually a variety of Saccharomyces cerevisia. Natural yeasts on the skins of the grapes may be used, but in commercial production cultured yeast is often used to give more predictable results. The amount of sugar in the liquid during fermentation is measured with a saccharometer (a calibrated hydrometer).  3. Fermentation Fermentation is indeed the magic at play in the making of wine. Many winemakers prefer to intervene at this stage by inoculating the natural must. Fermentation can require anywhere from ten days to a month or more. Sweet wine is produced when the fermentation process stops before all of the sugar has been converted into alcohol.  4. Clarification Once fermentation is completed, the clarification process begins. Filtering and fining may also be done at this stage. Often, winemakers will add egg whites, clay, or other compounds to wine that will help precipitate dead yeast cells and other solids out of a wine. These substances adhere to the unwanted solids and force them to the bottom of the tank. The clarified wine is then racked into another vessel, where it is ready for bottling or further aging.  5. Aging and Bottling The final stage of the wine making process involves the aging and bottling of wine. After clarification, the winemaker has the choice of bottling a wine immediately. Further aging can be done in bottle, stainless steel or ceramic tanks, large wooden ovals, or small barrels, commonly called barriques. The choices and techniques employed in this final stage of the process are nearly endless, as are the end results. However, the common result in all cases is wine. Enjoy!  Why is acid balance (pH) important in wine making? Fruit, including grapes, contain different types of acids. Too much acid renders a wine undrinkable. On the other hand, if wine does not have enough acidity, the result is a flat or insipid tasting wine. That's why it's important to check the acid levels and adjust if necessary.  Why is sulphite added in wine? Arrest fermentation at a desired time As preservatives to prevent spoilage and oxidation at several stages of the winemaking. Sulfur dioxide (SO2) protects wine from not only oxidation, but also from bacteria.  Why is clean equipment important in wine-making? Unwanted bacteria will compete with the wine-making yeast and have the potential to ruin the wine  How is sweet wine produced? Sweet wine is produced when the fermentation process stops before all of the sugar has been converted into alcohol. Does wine ‘go off ’ if left exposed to air? Yes, especially red wine. The wine gets oxidized. That is why some serious wine connoisseurs either finish a bottle of wine or they have a re-corking system that replaces any air with nitrogen.  Questions 1. Which grain is most often used to make beer? 2. How is the beer colour derived? 3. What are the two important by-products of fermentation? 4. In the winemaking process, what is the name for the crushed grapes and juice? 5. What gives red wines their dark colour? FERMENTED FOODS  YOGURT Milk from cows, sheep or goats may be used to prepare yoghurt. Yogurt usually use mixture of 2 cultures: Streptococcus thermophilus and Lactobacillus bulgaricus Fermented at 28-32 °C  Yogurt Making On a commercial scale the fat and protein content of the milk is adjusted and the milk is homogenized “This is a mechanical process which breaks up fat droplets and prevents them from separating out”. The milk is then pasteurized “process of heating milk up and then quickly cooling it down to eliminate certain bacteria”) and fermented by adding a ‘starter culture’ of bacteria, usually a mixture of Streptococcus thermophilus and Lactobacillus burgaricus. These bacteria act on the milk sugar, lactose and convert it to lactic acid which, in turn coagulates the milk protein, casein to produce the thick creamy consistency of yoghurt.  Cont’ The fermentation works best at a temperature of 40oC and, when complete, the yoghurt is cooled to 5oC to stop the bacterial processes. The lactic acid gives the yoghurt its slightly sour taste. Throughout the process, the materials and containers must be kept in a sterile condition, i.e. free from any micro-organisms that might compete with the Streptococcus thermophilus and Lactobacillus burgaricus and produce unwanted substances.  Acid produced from the fermentation causes the protein in the milk (casein) to coagulate into a semisolid curd  If you want strawberries or peaches, you must add them after the yogurt is made  Health Benefits of Yogurt 1. Helps in boosting one's immune system. 2. Helps in fighting Candida yeast infections. 3. Is rich in calcium and thus, keeps the bones strong and reduces the risk of osteoporosis. 4. Has anti-inflammatory properties. 5. Heals skin disorders faster. 6. Aids in keeping eating disorders in check.  Cheese-making Milk is homogenized, pasteurized and cooled to around 300C and add the starter culture. Pasteurization: a process that destroys pathogens through simple heat. Acidification: Starter culture is added to milk to change lactose (milk sugar) into lactic acid. This process changes the acidity level of the milk and begins the process of turning milk from a liquid into a solid called curdling. Coagulation: Rennet is added to further encourage the milk to solidify. Curds and Whey: Curds are cut using a knife or a tool that resembles a rake. Cutting the curds further encourages them to expel liquid, or whey.  Cont’ Rennet, which was traditionally obtained from the stomach of unweaned calves. It reacts with the casein protein in the milk to convert it into curd, the main element of cheese. After Cutting …… Cooking : After the cutting step the curd is cooked. This is done to expel moisture. Draining : Once a fairly solid mass of curd is obtained, it is pressed to expel further whey. This either done in block forming towers (dry salt production) or collected in moulds and pressed further (brine salt production). Salt is added before this process in dry salt production while brine salt production sees the cheese being immersed in a brine solution after being in moulds. Ripening :The cheese is left to ripen in a temperature controlled environment. This ripening period allows the various enzymes, acids and bacteria to spread throughout the cheese, developing each cheese's distinctive taste.  Bread Making In bread-making, cereal grain is crushed to form flour, thus exposing the stored starch. Water is added (making a dough) to activate the natural enzymes, e.g. amylases, in the flour, which then hydrolyse the starch via maltose into glucose. Yeast, Saccharomyces cerevisiae, is added which uses the glucose as a respiratory substrate, producing carbon dioxide. This carbon dioxide forms small bubbles which become trapped in the dough; upon baking in an oven these expand giving the bread a light texture.  Cont’ A protein called gluten gives the dough a sticky, plastic texture which holds the bubbles of gas. Dough is often kneaded – a process which traps air within it. This not only helps to lighten the bread directly but also provides a source of oxygen so that the yeast can respire aerobically, producing a greater quantity of carbon dioxide. Some anaerobic respiration nevertheless takes place and the alcohol produced is evaporated during baking.  GASOHOL A mixture of gasoline and ethyl alcohol used as fuel in internal combustion engines. A fuel consisting of a blend of ethanol and unleaded gasoline, especially a blend of 10 percent ethanol and 90 percent gasoline. The ethanol is obtained by fermentation agricultural crops or crop wastes (sugar can, maize or potatoes) and their subsequent distillation.  Gasohol production 1. Growing and cropping sugarcane 2. Extraction of sugars by crushing and washing the cane. 3. The crystallizing out of the sucrose (for sale) leaving syrup of glucose and fructose called molasses 4. Fermentation of the molasses by Saccharomyces cerevisiae to yield dilute alcohol 5. Distillation of the dilute alcohol to give pure ethanol, using the waste bagasse as a power source  Cont’ Molasses- the thick brown uncrystallized syrup obtained from sugar during refining Bagasse – once the sugar is extracted from the sugar cane, the fibrous waste is called bagasse. Used as a source of cellulose for some paper products and can be dried and burnt as power source for distillery. BIOGAS ENERGY  WHAT IS BIOGAS? Biogas is a methane rich flammable gas that results from the decomposition of organic waste material. Biogas Energy is the use of biogas to produce heat or power  ANIMAL MANURE DIGESTER The Anaerobic Digestion of animal waste creates methane. A container known as a digester is filled with appropriate waste (domestic rubbish, sewage or agricultural waste can be used) to which is added a mixture of many bacterial species, e.g. Methanobacterium spp. The anaerobic fermentation of these wastes yields methane, which is collected ready for use for cooking, lighting or heating.  The remaining solids can be used for: Fertilizer Animal bedding (sterilized of all pathogens)  BIOGAS MAY BE USED TO PRODUCE HEAT AND POWER The cleaned methane can be piped to an engine or turbine and generator to produce electricity or sent through the pipeline as a usable gas. Wastewater Treatment  Where does it all go! Where does the When you flush the water from the toilet where does the washer go? contents go? By gravity flow, the waste is on its way to your local wastewater treatment plant!  Sewage Plant Sewage contains all the waste from the baths, sinks, and lavatories of homes and factories. A sewage plant makes the water safe to be passed back into the waterworks.  Stages of wastewater treatment Primary : This is only a physical separation to remove solid matter. Effluent is allowed to settle for a few hours. Secondary : The organic and nutrient load is decreased by microbial activity or biological treatment.Up-to 95% so that the effluent is of a quality to be able to go into rivers. Tertiary : This is a complete treatment, but it is very expensive and not used much. When the treatment is done: Sludge – very nutrient rich is applied directly to land as fertilizer Advantage of the anaerobic bio-digester 1. The bulk of the sludge is greatly reduced. 2. The high temperatures of anaerobic fermentation destroy potential pathogens so that the residue can be safely used as a soil conditioner or compost and the remaining liquid can be used or sold as a liquid fertilizer. 3. The odours are greatly lessened (particularly valuable in intensive cow or pig farms). 4. Dumping of sludge is reduced and the potential for water pollution with farmyard slurry is avoided. 5. The methane (‘biogas’) is a valuable, relatively non- polluting source of energy.  Summary Biotechnology is the application of living organisms, systems or processes in industry Many biotechnological processes use micro-organisms (fungi and bacteria) to bring about the reactions Most biotechnological processes are classed as ‘ fermentations’. Fermentation may be aerobic or anaerobic. Beer and wine are produced from fermented sugars using yeast. Hops is a plant, the flowers of which give the bitter flavour and aroma to beer.  Cont’ Antibiotics are produced from bacteria and fungi Sterile condition are essential in biotechnology to avoid contamination by unwanted microbes. Yoghurt and cheese are made from fermented milk using bacteria Bacteria and protozoa play an essential role in the purification of sewage.  Cont’ Fermentation: Fermentation in food processing typically is the conversion of carbohydrates (sugar) to alcohols and carbon dioxide or lactic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions used for making certain foods. Beer: Alcoholic beverage made from barely grain that has been fermented by the yeast Wine: The grape juice is fermented with the help of Saccharomyces cerevisiae  Cont’ Biogas: Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. It is a mixture of methane and carbon dioxide, produced by anaerobic digestion of organic waste matter, used as a fuel Methane: It is a fuel which is produced by anaerobic fermentation from the wastes yields. Gasohol: Gasohol a gasoline substitute consisting of 90% gasoline and 10% grain alcohol by fermenting agricultural crops or crop wastes Sewage: Waste matter carried away in sewers or drains  Cont’ Cheese: Milk is treated with lactic acid bacteria and an enzyme called rennin that partially hydrolyses the protein and causes it to coagulate into “curds.” The liquid portion of the milk at this time is called “whey.” The whey is separated from the curds, and the curds are aged (“ripened”) Different microbes in the early and late stages of processing give rise to cheeses with different characteristics  Question 1. In which food would you find lactic acid bacteria? Mention some of their useful applications. 2. What organism is used to make yogurt? 3. Name the first organic acid produced by microbial fermentation. 4. Lactobacillus usually grows in _______ and produce ________ 5. Name the compound found in biogas. 6. Name the compound found in gasohol. 7. What kinds of microorganisms are employed in the treatment of sewage? Give their activities. 8. What are the different uses of biogas? 9. Explain the working of a biogas plant. END