Optimization of 4-aminobutyric acid feeding strategy and clustered regularly interspaced short palindromic repeats activation for enhanced value-added chemicals in halophilic Chlorella sorokiniana

Chlorella sorokiniana (CS) is a prominent microalga with vast potential as a biocarrier for carbon mitigation toward a green process. However, challenges remain in achieving high biomass levels and production rates. Therefore, a systematic feeding strategy using 4-aminobutyric acid (GABA) and CRISPR technology was applied to improve microalgal productivity. At first, GABA increased protein content by 1.4-fold, while intermittent supplementation during cultivation resulted in a 1.58-fold and 2.13-fold increase in biomass and pigment content, respectively. Under halophilic conditions, the optimal approach involved repeated feeding of 5 mM GABA at the initial and mid-log phases of growth, resulting in biomass, protein, and pigment levels of 6.74 g/L, 3.24 g/L, and 49.87 mg/L. CRISPRa mediated glutamate synthase and using monosodium glutamate (MSG) as a cheap precursor for GABA has effectively enhanced the biomass, protein, and lutein content, thus offers a cost-effective approach to commercialize high-valued chemical using algae towards a low-carbon paradigm.