Developing a heterotrophic fed-batch cultivation strategy for high-yield arginine-rich protein production using Chlorella vulgaris UTEX 395 and nutritional evaluation.

BACKGROUND: Chlorella sp. are promising candidates due to their rapid growth, high protein content (>400 g kg-1), and lower land/water requirements compared to conventional crops. However, autotrophic cultivation is limited by low biomass, which hinders large-scale application. Heterotrophic cultivation of Chlorella typically yields low protein content (<400 g kg-1) and limited arginine, a conditionally essential amino acid critical for juveniles and aquaculture species. In this study, Chlorella vulgaris UTEX 395 was screened as a potential strain for the production of high-value arginine-rich protein. Additionally, the heterotrophic fed-batch strategy using C. vulgaris UTEX 395 offers a feasible and effective approach for producing high-yield superior protein. RESULTS: C. vulgaris UTEX 395 cultivated in HA-SK medium achieved the highest biomass (14.12 g L-1), protein content (355.7 g kg-1), and arginine (38.0 g kg-1) among the five Chlorella strains. After fed-batch cultivation under screened favorable nutrient supply conditions, this microalga attained 19.26 g L-1 biomass with 509.7 g kg-1 protein and 66.0 g kg-1 arginine of dry biomass. Moreover, the established process was further evaluated in the 100 L fermenter. At the end of cultivation, the biomass of C. vulgaris reached 52.3 g L-1, with a protein content of 555.0 g kg-1 and arginine content of 83.2 g kg-1. Furthermore, C. vulgaris UTEX 395-derived protein and arginine were higher than those of other Chlorella species, soybean, egg, and fish meal. CONCLUSION: C. vulgaris UTEX 395 cultivated by the established heterotrophic fed-batch strategy is a potential candidate to produce high-value protein with a high level of arginine for food and animal feed applications. © 2026 Society of Chemical Industry.