Improvement of caffeic acid biotransformation into para-hydroxybenzoic acid by Candida albicans CI-24 via gamma irradiation and model-based optimization.

Singab, Raghda Abdelnasser; Elleboudy, Nooran Sherif; Elkhatib, Walid Faisal; Yassein, Mahmoud Abdulmajid; Hassouna, Nadia Adelhaleem

Para-hydroxybenzoic acid (PHBA) has great potential in biological applications due to its putative antiviral activity against SARS-CoV-2 and its antimicrobial activity in the face of the radically increasing number of multidrug-resistant pathogens. This is in addition to its anti-mutagenic, anti-inflammatory, antioxidant, hypoglycemic, anti-estrogenic, and anti-platelet aggregating activities. In this study, an approximate 6-fold increase in the production of PHBA was achieved via biotransformation of caffeic acid by C. albicans. The improvement was performed in two steps: first, through mutation by gamma irradiation (5 KGy dose), resulting in the recovery of a mutant (CI-24), which produced approximately triple the amount of PHBA produced by the wild-type isolate. Then, biotransformation by this mutant was further optimized via response surface methodology model-based optimization. The maximum PHBA production (7.47 mg/ml) was obtained in a fermentation medium composed of 1% w/v yeast extract as a nitrogen source, with an initial pH of 6.6, incubated at 28°C at an agitation rate of 250 rpm. To further enhance the performance and economics of the process, cells of the CI-24 mutant were immobilized in calcium alginate beads and could retain an equivalent biotransformation capacity after three successive biotransformation cycles. This article is protected by copyright. All rights reserved.