Enhancing bioactivity of Chlorella vulgaris through enzymatic pretreatment and lactic acid fermentation

Abstract This study explores an integrated bioprocessing approach to enhance the bioactivity of Chlorella vulgaris biomass through enzymatic pretreatment and lactic acid fermentation. Three pretreatment strategies—ultrasound-assisted hydrolysis, hydrothermal treatment, and enzymatic hydrolysis using Viscozyme, Alcalase, or their combination- were evaluated for their ability to release fermentable sugars and proteins. Enzymatic hydrolysis proved most effective, yielding up to 151.18 mg g DW− 1 of reducing sugars and 14.4 mg g DW− 1 of protein. Subsequent fermentation with Lactiplantibacillus plantarum and Levilactobacillus brevis demonstrated robust microbial growth (Δ log CFU ≈ 4.0) and significant acidification (pH 3.6–4.2), accompanied by lactic acid production up to 17.35 g/L. Functional characterisation revealed that combined enzymatic pretreatment and fermentation improved antioxidant properties, reaching values of 8.64, 19.46, 1.45 mg Trolox g DW⁻¹ in the CUPRAC, ABTS, and DPPH assays, respectively, while TPC reached 9.67 GAE g DW⁻¹. Moreover, Viscozyme-pretreated, L. plantarum-fermented samples showed inhibitory zones under non-neutralised screening conditions against Gram-positive bacteria. These findings highlight the combined effect of enzymatic pretreatment and microbial fermentation in enhancing the biofunctional value of C. vulgaris, offering a sustainable strategy for developing natural antioxidants and antimicrobial agents for food, nutraceutical, and cosmetic applications. Graphical Abstract