Microbial fermentation technology, with modern fermentation technology as its core, utilizes the metabolic activity process of microorganisms to produce various industrial fermentation products on a large scale through biotransformation. It has formed an independent industrial system with a wide variety and complete categories, and occupies an important position in the national economy.

Industrial fermentation refers to industrial production achieved through the life activities of microorganisms.
In industrial production, all industrial production that relies on the life activities of microorganisms is generally referred to as fermentation. This definition of fermentation is' industrial fermentation '. Microorganisms are the soul of industrial fermentation, without microorganisms there would be no industrial fermentation.
Industrial fermentation is the process of converting fermentation materials into microbial products that humans need through the life activities of microorganisms.
Industrial fermentation relies on the life activities of microorganisms, which are supported by the metabolic energy provided by biological oxidation. Therefore, industrial fermentation should cover all modes of biological oxidation in microbiology: aerobic respiration, anaerobic respiration, and fermentation.
In the past century, with the advancement of science and technology, industrial fermentation has undergone epoch-making changes. It has moved from the stage of using natural microorganisms for fermentation production to a new stage of transforming microorganisms with special X-energy according to human wishes to produce fermented products needed by humans.

Production type stainless steel fermentation tank
(1) The study of industrial fermentation begins with typical industrial fermentation
The more common industrial fermentation generally meets the following three conditions:
① The strains used belong to chemoheterotrophic microorganisms,
② The target product belongs to primary metabolites or energy metabolism by-products,
③ The target product is secreted outside the cell after being generated inside the cell.
Industrial fermentation that meets the above conditions is called typical industrial fermentation.
The study of industrial fermentation theory begins with typical industrial fermentation.
A systematic study of the theory of industrial fermentation of chemoheterotrophic microorganisms;
The second step is to systematically study the theory of industrial fermentation of other nutritional types of microorganisms;
The third step is to systematically study the theory of microbial utilization of non carbon elements in industrial fermentation.
(2) Industrial Fermentation Theory
The step-by-step study established three basic hypotheses for microbial life activities (the three hypotheses of fermentation). They are the theoretical basis for the transformation and utilization of microorganisms. Using these three basic assumptions to analyze typical industrial fermentation, the following appears:
① A new approach to microbial bio machines for industrial fermentation,
② Several inferences on industrial fermentation serving industrial production,
③ The "Five Word Strategy" for Industrial Microbial Breeding and Fermentation Process Control.
(3) Ideas for studying industrial fermentation

Industrial Fermentation → [From General to Special] → Typical Industrial Fermentation → [From Special to General] → Conceptual Models of Biological and Cellular Machines → [In Depth Research to Discover Natural Laws] → Natural Laws (Three Basic Hypotheses of Microbial Life Activities) → [From General to Special: Applying Natural Laws to Typical Industrial Fermentation] → Metastable Logistics Mode of Cellular Machines → Carrier Flow Path → Five Stage Method → Five Word Strategy → [From Special to General] → Prediction of Future Fermentation Industrial Production
Every 'action' involved in the growth and reproduction of microbial cells, including the initiation of organic matter degradation within the cell, the initiation and continuation of biosynthesis, active transport, pH automatic dynamic balance, etc., requires metabolic energy support. Maintaining cell life also requires metabolic energy support.
The material metabolism and energy metabolism of microbial cells are achieved through metabolic networks. Compounds flow in metabolic networks, forming metabolic streams. In industrial fermentation, the metabolic stream of raw materials is transformed into the target product through a series of pathways in cellular machines. On this basis, the second hypothesis of fermentation proposes that metabolic pathways and transport systems are integrated at the molecular level of metabolites and coordinated at the level of co factors, forming a metabolic network that spans both inside and outside of living microbial cells. This metabolic network is not simply connected by biochemical pathways and transmembrane transport processes, but rather incorporates biochemical concepts into the overall framework of cellular metabolism. The book mainly studies the metabolic network of organic matter (carbon element) at the enzyme and protein levels. Research has found that for facultative anaerobic microorganisms, not only are there significant differences in metabolic networks between aerobic and anaerobic periods, but their metabolic networks also vary when they survive under different culture conditions. For example, the metabolism of aerobic growth is built on the basis of the central plate with TCA ring as the skeleton, while during hypoxic growth, it is built on the basis of the central plate with TCA branching pathway at OAA as the skeleton.
In fact, microbial life activities can be divided into four levels: DNA level, protein level, logistics level, and microbial cell level, which need to be activated step by step. The metabolic network is scale-free, and the working mode of microbial cellular machinery describes the current carrying path of the cellular machinery during operation as a "channel" that connects the centripetal pathway, central pathway, and centrifugal pathway in sequence. As a metabolic network hypothesis, industrial fermentation is feasible and can predict the feasibility of developing new products and raw materials.
Structure determines function. Horizontally, the direction of the steps is to maximize the use of nutrients and achieve relatively large growth. Prokaryotes in eukaryotic cells do not have nuclei, so DNA receives regulatory signals from the cytoplasm. Therefore, the on/off control of protein synthesis is separated by the transcriptional membrane into different spaces, providing the possibility for separate regulation of synthesis metabolism and catabolism. The lactose operon in Escherichia coli is the operon of the enzyme system that controls the lactose degradation pathway. The negative and positive control of transcription initiation can respectively promote transcription - determining the level of enzymes involved in synthesis - and prevent transcription - preventing waste when glucose and lactose coexist. In addition, the regulation modes of inhibition and activation in microbial metabolic pathways, as well as the regulation modes of induction and inhibition of pathways, are very "smart" automatic regulation by these microorganisms themselves, which enables them to better adapt to survival. This is not subject to human subjective will, as stated in the third hypothesis "Cell Economy Hypothesis", microbial cells are an economic system formed through natural selection, serving as the guarantee system for microbial cell survival, providing security for cell adaptation X, economic X, and metabolic sustainability X.
From this perspective, microbial cells share the same characteristics as independent and self financing enterprises, which are very vivid. Three hypotheses support the normal operation of the "cellular machine" in the fermentation industry from three perspectives: energy, matter, and information. The three hypotheses gradually reveal the principle that microorganisms work well in the fermentation industry. Since microbial live cells are the microbial biological machines on the fermentation production line, they are autonomous cellular machines that store biological information. We need to increase our "dialogue" with microbial cells, exert subjective initiative, follow and utilize inherent operating laws (natural laws), handle the contradictory and unified relationship between humans and microorganisms in fermentation, promote cooperation, and obtain benefits.
Microbial fermentation process, also known as microbial reaction process, refers to the biochemical reaction process caused by the growth and reproduction of microorganisms.

According to the different types of microorganisms (aerobic, anaerobic, and facultative anaerobic), they can be divided into two categories: aerobic fermentation and anaerobic fermentation.
(1) Aerobic X fermentation requires constant exposure to a certain amount of sterile air during the fermentation process, such as using Aspergillus niger for citric acid fermentation, using Bacillus subtilis for glutamic acid fermentation, using Pseudomonas aeruginosa for polysaccharide fermentation, and so on.

aerobicstainless steelfermentation tank

(2) Anaerobic X fermentation does not require air supply during fermentation, such as lactic acid fermentation caused by lactobacilli, acetone and butanol fermentation caused by Clostridium difficile, etc.

Anaerobic stainless steel fermentation tank

(3) The facultative X fermentation yeast is a facultative X anaerobic microorganism that accumulates alcohol through anaerobic X fermentation under anaerobic conditions, and undergoes aerobic X fermentation under aerobic or ventilated conditions, reproducing a large number of bacterial cells.

Anaerobic stainless steel fermentation

According to the equipment, fermentation can be divided into open fermentation, closed fermentation, shallow fermentation, and deep fermentation.
Generally, open fermentation is applied to types that reproduce rapidly and undergo aerobic fermentation, such as yeast production. Due to the rapid and massive proliferation of its bacterial cells, it can inhibit the growth of other miscellaneous bacteria. So open fermentation equipment requires simplicity. On the contrary, closed fermentation is carried out in sealed equipment, so the equipment requirements are strict and the process is also relatively complex. Shallow plate fermentation (surface culture method) is the process of using a shallow plate to hold only a thin layer of culture medium, followed by surface culture after introducing the bacterial strain, to form a layer of bacterial film on top of the liquid. When there is a lack of ventilation equipment, this method can be used for some fast-growing aerobic microorganisms. Deep fermentation method refers to the microbial cultivation process carried out inside a liquid culture medium (not just on the surface).
Liquid deep fermentation is a technology developed in the production of antibiotics such as penicillin. Compared with other fermentation methods, it has many advantages:
① The liquid suspension state is a suitable growth environment for many microorganisms.
② In liquid, bacterial cells, nutrients, and products (including heat) are easily diffused, allowing fermentation to occur under homogeneous or quasi homogeneous conditions, making it easy to control and expand production scale.
③ Liquid transportation is convenient and easy to operate mechanically.
④ The factory has a small area, high production efficiency, easy automation control, and stable product quality.
⑤ The product is easy to extract and refine. Therefore, liquid deep fermentation is widely used in the fermentation industry
Commonly used microorganisms in industrial production
Microbial resources are abundant and widely distributed in soil, water, and air, with soil being particularly abundant. Some microorganisms can be utilized after being isolated from nature, while others require artificial mutagenesis of the isolated wild strains to obtain mutant strains before they can be utilized. The overall trend of bacterial strains used in the current fermentation industry is to shift from wild strains to mutant strains, from natural breeding to metabolic control breeding, and from inducing gene mutations to targeted breeding through gene recombination. The commonly used microorganisms in industrial production are mainly bacteria, actinomycetes, yeast, and mold. Due to the development of fermentation engineering itself and the introduction of genetic engineering, algae, viruses, etc. are gradually becoming microorganisms used in industrial production. Other microorganisms include basidiomycetes and algae.
【 EM 】 Commonly used bacteria in microbial fermentation technology
Microbial fermentation often varies depending on the strain and product, but the general process is basically the same, usually including strain preparation, raw material processing, inoculation culture, fermentation control, and product extraction.
1. Preparation of bacterial strains
Bacteria are the mother of fermentation industry. Without bacteria, there can be no microbial fermentation. The bacterial strains are generally divided into preserved bacterial strains, shake flask (eggplant bottle, etc.) bacterial strains, and seed jar bacterial strains. Preserved bacterial strains are backup strains for fermentation production, usually stored in a low-temperature dry state. Before the preservation of bacterial strains enters production inoculation, they are first connected to the inclined surface for activation, so that the strains can transition from a dormant state to a normal metabolic state. The culture medium used for activation is generally nutrient rich, easy to absorb, and beneficial for the growth and reproduction of bacterial strains. After activation, the bacterial strain is further expanded and transferred to a shaking bottle (such as an eggplant bottle) for cultivation. The culture used at this time is

Strain cultivation fermentation tank

The culture medium used for preserving bacterial strains is more extensive and economical. Shake the bottle seeds to further expand and transfer them to the seed tank for cultivation. The seed tank culture medium is relatively close to the composition of the culture medium used in the fermentation tank, with the aim of further adapting the bacterial strains to the environment of the fermentation medium. After the seeds are cultured in the seed jar, they can be inoculated in a large jar (ventilated chamber) at an appropriate time.