Biotechnological production of phenolic acids is attracting increased interest due to their superior antioxidant activity, as well as other antimicrobial, dietary, and health benefits. As secondary metabolites, primarily found in plants and fungi, they are effective free radical scavengers due to the phenolic group available in their structure. Therefore, phenolic acids are widely utilised by pharmaceutical, food, cosmetic, and chemical industries. A demand for phenolic acids is mostly satisfied by utilising chemically synthesised compounds, with only a low quantity obtained from natural sources. As an alternative to chemical synthesis, environmentally friendly bio-based technologies are necessary for development in large-scale production. One of the most promising sustainable technologies is the utilisation of microbial cell factories for biosynthesis of phenolic acids. In this paper, we perform a systematic comparison of the best known natural sources of phenolic acids. The advances and prospects in the development of microbial cell factories for biosynthesis of these bioactive compounds are discussed in more detail. A special consideration is given to the modern production methods and analytics of phenolic acids.

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Bilberry (Vaccinium myrtillus L.) pomace contains a significant amount of polyphenols and can serve as a basis for food additives, nutraceuticals, and functional foods. Although various techniques can be employed to recover bioactive fractions from berry pomaces, data on enzyme-assisted extraction (EAE) of bilberry pomace are rather scarce. This study aimed to optimize critical EAE parameters using Viscozyme L to obtain a high-yield extract with enhanced antioxidant capacity. Central composite design and response surface methodology evaluating the effect of four independent variables, namely, pH, temperature, extraction time, and enzyme concentration on three responses, were employed to define optimal EAE conditions. Under the optimal conditions (pH: 4.5, temperature 46 °C, 1 h of extraction, and 2 active units (AU) of Viscozyme L/g of pomace), EAE yielded 56.15 g/ 100 g DW of the water-soluble fraction. Comparison with conventional maceration indicated that EAE, besides the yield, significantly increased the in vitro antioxidant capacity measured by the total phenolic content, ABTS, ORAC, and CUPRAC assays. Moreover, an increase was observed for the measured mono- and disaccharide as well as anthocyanin content. Overall, this study demonstrates the improved efficiency of EAE over conventional solid–liquid extraction to recover fractions with a higher yield and enhanced functional properties in a fast and sustainable manner.