# Improved Functions of Fermented Coffee by Lactic Acid Bacteria
## 4 Discussion  
Fermentation improves the functionality of foods, and the fermentation process involves several parameters, like the type of microorganisms involved and their cell concentration enzymatic activities, and conditions like temperature, pH, and fermented media. In general, microbial fermentation is divided into four categories, viz., (i) the production of viable cellular material or the generation of biomass; (ii) the generation of metabolites; (iii) the synthesis of enzymes, proteins, and vitamins; and (iv) the production of value-added products from a substrate [25]. In our experiment, we observed the increased acidity and increased biomass of the fermented samples as compared to the non-fermented sample (control). As we used lactic acid bacteria strains CJNU 0441, CJNU 1844, and KNUT 0384, these strains were involved in the production of lactic acid, thus increasing the acidity of the fermented BV 20 brix coffee extract. Lactic acid bacteria are those that produce lactic acid as a major organic acid. Besides that, coffee naturally contains caffeic acids, quinic acids, and chlorogenic acids. The increased acidity could be due to the production of lactic acid by the starter culture and the breakdown of coffee metabolites into acid precursors during the fermentation process. Increased acidity in coffee can significantly alter its sensory properties, influencing both its flavor profile and the overall drinking experience. The increased acidity or low pH can enhance citrus and acidic flavors, which are typically desirable in coffee. However, it is essential to carefully monitor this parameter; excessively low pH levels can result in overly acidic or even disagreeable flavors. Thus, pH, acidity, and type of acid produced serve as a critical control point in the production of specialty coffees [33]. We also observed an increase in biomass in the fermented coffee extract. During fermentation, cells utilize a portion of the substrate and vital nutrients from the fermentation medium. Initially, the cells undergo multiplication and growth. The growth pattern can vary depending on the cell type, whether they are unicellular or molds. For instance, unicellular organisms, which divide when they grow, will increase the number of cells or increase the biomass. During fermentation, the cell mass of bacteria increases due to the production of new cells. In the process of fermentation, bacteria need energy for their metabolism and the production of organic acids such as lactic acids. The production of these compounds requires energy and building blocks that are obtained from carbohydrates. Therefore, bacteria need to produce new cells to maintain their population size and continue the fermentation process [34]. We observed the enhanced oxidative potential and antimicrobial activity of the fermented coffee extract against the Gram-positive bacteria _Listeria monocytogenes_ KCTC 3569 and _Streptococcus mutans_ KCTC 5244. The mechanism of the antibacterial activity of coffee extract is not well understood. However, coffee contains a wide range of chemicals that may be responsible for its antibacterial effect, such as complex combinations of phenolic compounds [9]. Depending on their composition and concentration, these phenolic chemicals may activate or inhibit microbial development [35]. It has also been observed that fermentation increases the content and bioactivity of phenolic compounds responsible for the anti-oxidative and antibacterial activities of coffee extract [36]. In our experiment, we also observed an increase in the content of phenolic acids, specifically chlorogenic acid. Our results match with the results of a study conducted by [PERSON] et al. [37] in which the CGA content was increased by 400% via solid-state fermentation of the coffee pulp with different yeast strains. There is a lack of data on the mechanism of increased CGA content during fermentation.