abstract
Microorganism is a precious and rich biological resource. Widely used in food, fermentation, pharmaceutical, environmental protection, metallurgy, agriculture and other industries. If this kind of resources can be further developed scientifically and reasonably, it will certainly create great material wealth for mankind. Food is the most important thing for people, and food is the foundation of human survival. In recent years, due to the increase of population and the improvement of living standards, the world has put forward higher requirements for the quality and quantity of food. With the continuous utilization of food resources, opening up new food resources has aroused more and more people's thinking. In the process of searching for new food resources, although people are used to focusing on expanding planting, animal husbandry and aquaculture, due to the unique characteristics of microorganisms, people have a strong interest in searching for new food resources and broaden their horizons. After continuous research and development, a large number of foods produced by microorganisms have been put on the market. Microbes play an increasingly important role in enriching food types, increasing or improving the content of nutrients and improving the flavor of food, showing broad application prospects, and gradually realizing the transformation of food from two-dimensional structure of plants and animals to three-dimensional structure of plants, animals and microorganisms.
main body
microbial fermentation
Nowadays, the main technology used by people is to make food through microbial fermentation. Microbial fermentation is a process of transforming raw materials into products needed by human beings through specific metabolic pathways by using microorganisms under suitable conditions. Microbial strains are the basic factors of fermentation. Through mutation and strain screening, high-yield excellent strains can be obtained, and products that are difficult to produce by conventional methods can be obtained by making full use of production equipment. There are three technological factors in fermentation: 1, temperature 2, PH 3 and oxygen.
Content of modern microbial fermentation engineering
(1) The industrialized microbial breeding technology, which uses modern means to screen and transform microorganisms to form new strains more in line with the needs of industrial production, permeates some contents of genetic engineering and cell engineering. The modified microbial strains that meet people's needs are usually called engineering bacteria;
⑵ The production of microbial cells refers to the use of advanced production technology, that is, the cloning of engineering bacteria, to carry out a large number of pure cultures of microorganisms at high speed;
(3) separating useful substances from microorganisms, such as using microorganisms to produce single-cell proteins with some cheap wastes as substrates;
(4) Fermentation to produce primary and secondary metabolites of microorganisms, such as amino acids, antibiotics and other physiologically active substances;
(5) separation, purification and post-treatment of fermentation products;
[6] using microorganisms to control or participate in industrial production, such as mining and metallurgy; And the research and development of microbial bioreactor, new fermentation device, biosensor and computer-controlled automatic continuous fermentation technology.
Microbes and Brewed Products
First, the application of acetic acid bacteria-producing vinegar
As we all know, vinegar is one of the condiments in our daily life, and it is also an ancient product produced by microorganisms in China. In the folk, the production of vinegar is naturally fermented by acetic acid bacteria existing in nature; In the factory, in order to improve the yield and quality, and avoid the pollution of miscellaneous bacteria, artificial pure inoculation is used for fermentation.
Acetobacter striatum (aceti Acetobacter) and Acetobacter Xu have long been used in vinegar production. But at present, the most widely used variety is Acetobacter malodorus. Turbidity (AS 1.4 1) and Acetobacter pasteurella subsp. Pasteurella (Lu Niang 1.0 1).
Acetobacter grows and reproduces under the condition of sufficient oxygen supply, and the ethanol in the substrate is oxidized into acetic acid, which is a biological oxidation process, and the reaction formula is omitted.
According to different strains, a small amount of other organic acids and aromatic esters can be produced in the fermentation process, which makes vinegar have a good flavor. Therefore, it is very important to select excellent strains for vinegar production.
The brewing methods of vinegar can usually be divided into two categories: solid fermentation and liquid fermentation. The traditional brewing methods in China mostly adopt solid fermentation. The vinegar produced by this method has good flavor, but it needs more auxiliary materials, long fermentation period, low utilization rate of raw materials and high labor intensity.
(1) raw materials
There are many raw materials available in vinegar production, such as grain, dried and fresh fruits, wild fruits containing sugar or starch, etc. For example: sugar, honey, sorghum, rice, corn, sweet potato, sugar granules, pears, persimmons, dates and so on. Generally, famous vinegar is mainly made of glutinous rice, rice, sorghum and other food raw materials.
(2) Process flow
Mixing raw materials → adding water, stirring and cooking → adding bran koji and alcohol after cooling → saccharifying and fermenting → inoculating acetic acid bacteria → acetic acid fermentation → aging with salt → pickling → aging (adding fat, seasoning, strengthening, coloring and increasing acetic acid to more than 5%) → blending → sterilization → packaging and finished products.
There are many kinds of vinegar produced in China and many famous products. Such as Shanxi mature vinegar, Zhenjiang fragrant vinegar, Sichuan bran vinegar, Jiangsu and Zhejiang rose vinegar, Fujian red yeast vinegar, Northeast white vinegar, etc. All kinds of vinegar have their own characteristics in material selection, fermentation technology, final blending and aging.
Second, amino acid fermentation
Amino acids are the basic components of protein. There are eight kinds of amino acids that cannot be synthesized in the body (human body), but they are necessary. Usually these eight amino acids are called essential amino acids, which can only be obtained by human body through food.
In addition, in the food industry, amino acids can be used as seasonings, such as sodium glutamate-monosodium glutamate. Tryptophan and glycine can be used as sweeteners. Adding certain amino acids to food can improve the nutritional value of food. For example, adding lysine to rice can improve the utilization rate of protein. In order to improve the feed quality of livestock, essential amino acids such as lysine and methionine are often added. Therefore, the production of amino acids is of great significance.
Initially, amino acids were produced by hydrolyzing protein. Since 1957 successfully produced glutamic acid by direct fermentation of carbohydrates by microorganisms and put it into industrial production, the research and production of amino acids have developed rapidly, and about ten kinds have entered industrial scale production. In China, glutamic acid fermentation began at 1963.
(a) the production of sodium glutamate (monosodium glutamate):
Glutamate fermentation bacteria: Corynebacterium glutamicum, Aspergillus ochraceus, etc.
Production strain used in China: Corynebacterium pekingense, as1.299; ; Corynebacterium crenatum, AS 1.542. The common characteristics of these bacteria are: the bacteria are spherical, short to rod-shaped, flagellate-free, immobile, gram-positive, require biotin for growth, and produce glutamic acid by aeration culture.
Biochemical process of glutamic acid fermentation: firstly, glucose generates pyruvate through glycolysis and hexose monophosphate branching, pyruvate → acetyl coenzyme A→ tricarboxylic acid cycle → α-ketoglutarate, and L- glutamic acid is generated under the action of glutamate dehydrogenase in the presence of NH4+.
1. raw materials: raw materials for producing sodium glutamate by fermentation include starch corn, sweet potato, wheat and rice, among which sweet potato starch is the most commonly used. In addition, molasses can also be used as a carbon source of fermentation medium. The nitrogen source can be urea or ammonia.
2, process flow:
Starch raw materials → saccharification → cooling and filtering → adding corn syrup and other nutrients to prepare a suitable culture medium → strain fermentation → fermentation → fermentation broth → extraction (isoelectric point method, ion exchange method, etc. ) → crystallizing glutamic acid → neutralizing →Na2CO3 → sodium glutamate (monosodium glutamate) → removing iron, decolorizing, filtering, concentrating, crystallizing (monosodium glutamate) → drying to obtain the finished product.
Three, vegetables and fruits of lactic acid fermented food
Vegetables and fruits can be fermented by lactic acid bacteria, which can not only obtain nutritious products with certain flavor, but also be a food processing method. At the same time, it is a time-honored food preservation method. With the gradual improvement of people's understanding of the nutritional value of fruit and vegetable lactic acid fermented food and its beneficial effects on human body, the lactic acid fermented processing industry of fruit and vegetable food has been developed, not only the variety has increased, but also the processing process has gradually moved from cottage industry to mechanized industrial production.
People in China have a long history of making fruit and vegetable products fermented by lactic acid, including delicious and nutritious pickles, sauerkraut, pickles with various patterns and flavors, fruit and vegetable juices fermented by lactic acid and so on.
Application of Yeast in Food Manufacturing
Yeast has a wide range of uses, mainly used in food manufacturing (wine and bread production), single cell protein, pharmaceutical and chemical industry (nucleic acid and vitamin production), petroleum hydrocarbon fermentation and so on.
Yeast is closely related to human life. For a long time, people used yeast to make food public relations, bread, wine and other foods. Therefore, yeast plays an extremely important role in food industry.
The application of yeast in food is introduced below.
Bread production
Bread and steamed bread are almost common foods for urban and rural people in China. They are all made of flour fermented by yeast. They are soft and delicious, but the bread is made of reasonable raw materials and baked, so it is more delicious and nutritious, and easy to carry and store.
Beer yeast used to make bread can be obtained from breweries, but there are professional factories to produce yeast products. Yeast products specially used for bread production include pressed yeast (fresh yeast) and active dry yeast (ADY), and pressed yeast is commonly used.
Bread is made of flour, mixed with water and yeast, and fermented at about 30℃. Yeast uses amylase in flour to decompose starch into wheat, glucose, fruit and sucrose, and produces products such as carbon dioxide, alcohol, aldehydes and some organic acids.
Carbon dioxide makes the dough swell, the fermented dough is kneaded and then added with ingredients, and then baked in a baking oven at high temperature. When carbon dioxide is heated and expanded, bread becomes a porous sponge structure, and the product is soft in texture. Organic acids, alcohols and aldehydes produced during fermentation give bread a unique flavor. Some also add various edible flavors, nuts, preserved fruits and other accessories to form different varieties of colors.
Application of Microbial Enzymes in Food Industry
Enzymes have been used in food manufacturing for a long time, but the understanding of enzymes is an important achievement of modern science. With the development of food industry, higher requirements are put forward for the variety, quantity and quality of enzymes. Therefore, countries all over the world attach great importance to the research and production of enzymes.
First, the advantages of microbial production of enzyme preparation
It is generally believed that M cells can produce at least 2500 different enzymes.
The production of microbial enzymes is selective (selecting strains), which is convenient for industrial production and is not limited by season, climate, geography and other conditions; The production capacity can also be unlimited, and the growth cycle of M is short, which can ensure the supply of enzymes.
Second, microbial enzyme and its application in food industry
1. Enzyme-producing microorganisms: Microbial enzyme preparations can be produced by bacteria, actinomycetes, yeasts, molds, etc.
2. Types of enzymes: There are many kinds of microbial enzymes, mainly amylase, protease, lipase, cellulase, pectinase and catalase. Various enzymes play different roles in food industry.
Application of fermentation engineering in food industry;
There are three main types of products. One is to produce traditional fermented products, such as beer, fruit wine and vinegar. The second is to produce food additives; The third is to help solve the food problem.
In the food industry, microorganisms are not only used to produce food, but also used as one of the detection indicators in food hygiene standards to judge the hygienic quality of food, so as to effectively ensure product quality, better guide consumption and protect human health.
In microbial fermentation, advantages and disadvantages coexist, and development and challenges coexist. What we have to do is to seek development by constantly developing science and technology, seeking advantages and avoiding disadvantages, and facing challenges directly. Although many products we enjoy today are inseparable from the traditional fermentation industry, modern microbial engineering has impacted various industries including traditional food fermentation industry, pharmaceutical industry, organic acid manufacturing industry, feed industry and so on.