Types of Fermentation: Definition, Process and Advantages

Fermentation is an essential metabolic process performed by many microorganisms, including as bacteria, yeast, and molds, that transform macromolecules, usually carbohydrates, into more basic chemicals. This process frequently takes place in the absence of oxygen, and as a result, it produces energy for the microbes. Fermentation is a crucial process in food production, medicine, and biotechnology as it enables the conversion of basic ingredients into edible items that have clearly defined tastes, textures, and health advantages. Engineered microbial fermentation offers three main benefits compared to multicellular (higher eukaryotic) tissue culture: Reduced need for meticulous growing conditions; notably accelerated growth cycles; and less ethical debate and market opposition in biomedical and food sector applications.

Fermentation technology at BOC Sciences

• Aerobic Fermentation
• Anaerobic Fermentation
• Continuous Fermentation & Fed-Batch Fermentation
• Solid State Fermentation (SSF)
• Submerged Fermentation (SmF)
• Fermentation CDMO

Lactic Acid Fermentation

Definition and Process: Lactic acid fermentation is the thermochemical conversion of carbohydrates, mainly glucose, into lactic acid by particular bacterial strains, such as Lactobacillus, or specific yeasts. The anaerobic type of fermentation, which takes place in the absence of oxygen, is essential for the synthesis of many fermented foods. Gram-positive, non-sporulating rods and cocci with low guanine-cytosine concentration are known as lactic acid bacteria. They are a class of organisms that convert sugar (glucose) to lactic acid. They are further classified into two subgroups: homo-fermentative and hetero-fermentative.

Advantages: Lactic acid fermentation of foods is commonly practiced in tropical countries due to its inherent advantages: (i) a cost-effective means of food preservation, inhibition of spoilage and pathogenic microorganisms through a combination of pH reduction, decreased oxidation-reduction potential, competition for essential nutrients, and the generation of inhibitory compounds such as antibiotic components and hydrogen peroxide; (ii) enhanced sensory qualities; and (iii) in certain instances, improvement in the nutritional value or digestibility of the raw material. Protease hydrolysis of lactic acid bacteria during fermentation resulted in modifications of protein molecules that enhanced the development of gels in soybeans, as well as increased the presence of hydrophobic peptides and hydrophobic amino acids. The process of fermenting pea protein in lactic acid was enhanced to reduce undesirable tastes. This was achieved by breaking down bigger peptides, which therefore reduced the solubility of the protein. Additionally, the use of lactic acid fermentation treatment enhanced the taste of pea proteins, as determined by descriptive sensory analysis.

Alcoholic Fermentation

Definition and Process: Alcoholic fermentation is the process, in which yeast, typically Saccharomyces cerevisiae, or certain bacteria, convert carbohydrates into ethanol and carbon dioxide. This anaerobic process is a long-standing and very significant kind of fermentation, especially in the food and beverage sector. The process of alcoholic fermentation involves the glycolysis of glucose to produce pyruvate, which is then transformed into ethanol and carbon dioxide. It is crucial for this process to take place in the absence of oxygen. The fermentation process is carried out by yeasts in various conditions, including dough and fruit juice, leading to the synthesis of alcoholic drinks and leavened bread. An inherent benefit of alcoholic fermentation is its capacity to generate ethanol, a crucial component not just for alcoholic drinks but also for biofuel manufacturing. Moreover, the carbon dioxide produced during this process is beneficial in the baking process, and the fermentation itself assists to preserve food by establishing a conducive environment that discourages the growth of spoiling microorganisms.

Advantages: The fundamental advantage of alcoholic fermentation is its capacity to create ethanol, which is required not only for alcoholic drinks but also for biofuel generation. Furthermore, the carbon dioxide produced during this process is important in baking, and the fermentation itself protects food by producing an environment that discourages spoiling germs.

Acetic Acid Fermentation

Definition and Process: Acetic acid fermentation is an aerobic process that predominantly entails the oxidation of ethanol into acetic acid. This process is carried out by bacteria from the Acetobacter genus. This form of fermentation is typically used in the production of vinegar and necessitates the presence of oxygen. Acetic acid fermentation necessitates oxygen, in contrast to other fermentation processes that are anaerobic. Bacteria oxidize ethanol, which may have been produced through alcoholic fermentation, into acetic acid during this process. This acidification is essential for the production of vinegar, which is renowned for its acidic flavor and preservative properties.

Advantages: The process of acetic acid fermentation in the creation of vinegar serves as a natural preservative and enriches the taste of many food products. Furthermore, its acidity inhibits the proliferation of some detrimental microorganisms, therefore enhancing food safety, while the fermentation process itself imparts distinctive and much sought-after tastes.

Butyric Acid Fermentation

Definition and Process: Butyric acid fermentation, which is mainly performed by Clostridium bacteria, involves the conversion of sugars and starches into butyric acid, as well as byproducts including carbon dioxide and hydrogen. This type of fermentation takes place in anaerobic circumstances and is known to produce strong aromas and tastes.

Advantages: Butyric acid fermentation is used in the creation of some varieties of cheese, contributing to the formation of distinct tastes. Beyond food production, butyric acid is employed in the creation of biofuels and as an industrial chemical precursor. The principal benefit of butyric acid fermentation is its usage in industrial applications, specifically the production of butyric acid for use in biofuels and other goods. Furthermore, in some cheeses, this fermentation helps to generate particular tastes that customers value.

Propionic Acid Fermentation

Definition and Process: Propionic acid fermentation is a metabolic process facilitated by Propionibacterium bacteria, wherein lactic acid is transformed into propionic acid, acetic acid, and carbon dioxide. Within the dairy sector, this anaerobic procedure plays a crucial role in enhancing the taste and texture of Swiss cheese.

Advantages: This fermentation process involves the metabolism of lactic acid, a byproduct of lactic acid fermentation, by bacteria to generate propionic acid. The emission of carbon dioxide during this procedure gives rise to the distinctive voids, commonly referred to as "eyes," in Swiss cheese, while the presence of propionic acid contributes to the cheese's nutty notes. Furthermore, propionic acid functions as a preservative by suppressing the proliferation of mold and spoilage microorganisms, therefore prolonging the product's shelf life.

Methane Fermentation

Definition and Process: Methanogenesis (Methane Fermentation) is an anaerobic fermentation process in which archaea (methanogens) transform organic substrates including acetate, carbon dioxide, and hydrogen into methane (CH₄).

Advantages: Methane fermentation is frequently utilized in biogas production, which involves fermenting organic waste materials in anaerobic digesters to produce methane, which may then be used as a renewable energy source. Methane fermentation also aids in waste management by lowering the volume of organic waste while providing valuable byproducts. Methanogenesis is a sustainable method for producing renewable energy from waste resources. This process produces methane, which may be trapped and utilized as a clean-burning fuel, so reducing greenhouse gas emissions and offering an alternative to fossil fuels.

Schematic representation of the common types of fermentation. (Vilela A., et al., 2019)

Different types of Fermentation on the basis of the end product formed. (Sun W., et al., 2022)

Summary

The process of fermentation has a diverse array of benefits in several sectors. Within the realm of food processing, it prolongs the duration for which perishable products may be stored by establishing acidic or alcoholic conditions that inhibit the proliferation of detrimental bacteria and fungus. Foods that have undergone fermentation frequently have improved nutritional characteristics, as fermentation can promote the absorption of vitamins and minerals. Moreover, certain fermented items, such as yogurt and kimchi, have probiotics that enhance the composition of the gut microbiota and provide benefits for digestive health. Fermentation is very energy-efficient, particularly in anaerobic environments, as it demands less external energy compared to other industrial processes.

References

1. Vilela A., et al., Beverage and food fragrance biotechnology, novel applications, sensory and sensor techniques: An overview, Foods, 2019, 8(12): 643.
2. Sun W., et al., Research progress of fermented functional foods and protein factory-microbial fermentation technology, Fermentation, 2022, 8(12): 688.