Stepwise processing of Chlorella sorokiniana confers plant biostimulant that reduces mineral fertilizer requirements

We developed a stepwise method to transform Chlorella sorokiniana microalgal biomass into a potent biostimulant. The method, including maceration, high-pressure homogenization, and enzymatic hydrolysis, preserves the bioactive properties of the biomass as a biostimulant while minimizing plant inhibitory effects. Fractions were characterized individually, and optimal concentrations were determined using a rapid Arabidopsis root assay. A blend of optimal concentrations of fractions was identified as the most stimulating extract, increasing the root elongation by 25 %. When applied to tomato plants and monitored using high-throughput plant phenotyping, the blend displayed a 25 % reduction in mineral fertilizer use. Metabolomic analysis of the tomato plants showed significantly enhanced carbon and nitrogen metabolism in the leaves. Our findings indicate that the stepwise processing not only produces an effective biostimulant but also generates substantial residual biomass for a potential multiproduct biorefinery approach that can improve the overall techno-economic outlook.