Lactic Acid Fermentation: Definition, Equation,Examples and Benefits

Lactic acid fermentation definition

Lactic acid is an organic acid that is naturally occurring and can be synthesized through chemical synthesis or fermentation. Lactic acid fermentation is a type of anaerobic respiration where sugars (primarily glucose) are converted into cellular energy and lactic acid by lactic acid bacteria (LAB) or other microorganisms. The biotechnological production of lactic acid through fermentation offers a substantial advantage over chemical synthesis in that it can utilize cost-effective raw materials, including glucose, starchy residue, cellulosic, and other carbohydrate-rich materials. The cost of raw materials is a significant factor to consider in the economic production of lactic acid. However, the ultimate efficiency and economics of lactic acid fermentation remain a challenge from numerous perspectives, and media compositions are crucial in the enhancement of this process. Additionally, the biotechnological production of lactic acid provides numerous advantages over chemical synthesis, including low substrate costs, low production temperatures, and low energy consumption, in addition to the high product specificity that is achieved by producing a desired optically pure l-(+)- or d-(−)-lactic acid.

Fermentation technology at BOC Sciences

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

Overview of lactic acid production through chemical synthesis and microbial fermentation. (Ahmad A., et al., 2020)

Lactic acid fermentation equation

The basic chemical equation for Lactic acid fermentation, where glucose is converted into lactic acid, is as follows: C₆H₁₂O₆ (glucose)→2C₃H₆O₃ (lactic acid) +2 ATP.

Comparison of chemical and fermentation production of enantiopure lactic acid. (Hoyos P., et al., 2017)

Lactic acid fermentation examples

Several well-known fermented food items rely heavily on lactic acid fermentation as part of their manufacturing processes:

Yogurt: Lactic acid bacteria, such as Lactobacillus bulgaricus and Streptococcus thermophilus, ferment lactose, or milk sugar, to produce lactic acid, which is then used to make yogurt. This gives the yogurt its distinct sour flavor in addition to thickening the milk by inducing proteins to coagulate.

Sauerkraut: Finely shredded cabbage undergoes fermentation by Leuconostoc, Lactobacillus, and other lactic acid bacteria, resulting in the production of lactic acid. This acid serves to preserve the cabbage and imparts a sour flavor.

Kimchi: A conventional Korean fermented vegetable dish, usually prepared with napa cabbage, subjected to fermentation by lactic acid bacteria (LAB), resulting in its signature sour and spicy taste.

Pickles: Cucumbers undergo lactic acid fermentation, a process in which lactic acid bacteria decompose carbohydrates into lactic acid, therefore preserving the pickles and imparting their distinctive sour taste.

Sourdough Bread: Lactic acid bacteria and yeast are both necessary for the fermentation of dough in sourdough bread, which results in the production of lactic acid and gives the bread its unique sour flavor.

Kefir: It is a fermented milk beverage created by infusing milk with kefir grains, which contain a symbiotic culture of lactic acid bacteria and yeasts. Lactose is fermented into lactic acid, carbon dioxide, and trace quantities of ethanol, yielding a sour, slightly effervescent beverage high in probiotics. Kefir is recognized for its digestive advantages and is simpler to digest for people who are lactose intolerant since lactose is broken down during the fermentation process.

Fermented Fish: In certain civilizations, fish is preserved via lactic acid fermentation. Surströmming, a Swedish delicacy, is prepared by fermenting Baltic herring with salt, allowing lactic acid bacteria to convert the fish's carbohydrates into lactic acid. Another example is pla-ra, a Thai fermented fish product that is fermented with lactic acid in a saltwater brine. These fermented fish items have a strong, pungent odor and a characteristic sour flavor.

Applications of fermentation technology at BOC Sciences

• Fermentation in Pharmaceuticals
• Fermentation for Special Small Molecules
• Fermentation in Human Nutrition
• Fermentation in Animal Health
• Fermentation in Agriculture
• Fermentation for Pigments
• Fermentation for Feed Additives

Benefits of lactic acid fermentation

Preservation: Lactic acid fermentation has been used to preserve food for many millennia. Lactic acid generation lowers the pH of the food, resulting in an acidic environment that prevents the growth of hazardous pathogens and spoilage organisms, increasing the shelf life of fermented items without the need for refrigeration or artificial preservatives.

Improved digestive health: Lactic acid fermentation produces foods that are high in probiotics, which are helpful microorganisms that maintain a healthy gut microbiota. Fermented foods such as yogurt, kefir, and sauerkraut can help balance gut flora, increase digestion, and alleviate the symptoms of digestive diseases like irritable bowel syndrome (IBS) and constipation.

Enhanced nutrient absorption: Lactic acid fermentation can improve nutritional bioavailability by converting complicated molecules into more digestible ones. For example, the fermentation of soybeans in products like tempeh increases the availability of protein and some vitamins (such as B vitamins), making them easier to absorb.

Boosted immune function: Lactic acid-fermented foods can boost immune function by increasing gut health, which is critical for immunological control. Probiotics included in fermented foods can improve the intestinal barrier, preventing dangerous bacteria from entering the body and generating an immune response.

Reduction of antinutrients: Antinutritional elements like phytic acid and lectins, which can prevent the absorption of crucial minerals like calcium, magnesium, and iron, are decreased by lactic acid fermentation. For instance, these antinutrient levels are lowered during the fermentation of grains and legumes, which enhances overall nutrition by facilitating improved mineral absorption.

Flavor and texture enhancement: Foods that undergo lactic acid fermentation acquire a distinct sour flavor that can improve the flavor profile of a variety of cuisines. Food texture can also be enhanced, as seen by the tangy, crisp pickled veggies or the creamy, yogurt-like consistency.

Lactose reduction in dairy products: Lactose, the sugar present in milk, is broken down into lactic acid by lactic acid bacteria during the fermentation process of dairy products. For those who are lactose intolerant, this procedure improves the digestion of fermented dairy products like kefir and yogurt.

References

1. John R P., et al., Direct lactic acid fermentation: Focus on simultaneous saccharification and lactic acid production, Biotechnology advances, 2009, 27(2): 145-152.
2. Ahmad A., et al., A review on the lactic acid fermentation from low-cost renewable materials: Recent developments and challenges, Environmental Technology & Innovation, 2020, 20: 101138.
3. Hoyos P., et al., 3.28 - Biocatalyzed Production of Fine Chemicals [M]//MOO-YOUNG M. Comprehensive Biotechnology (Third Edition). Oxford; Pergamon. 2017: 334-73.