title: Nitrate concentration-shift cultivation to enhance protein content of heterotrophic microalga Chlorella vulgaris: Over-compensation strategy.
abstract: Protein production from microalgae requires both high cell density during cultivation and high protein content in cells. Heterotrophic microalgae can achieve high cell density, and yet are confronted with the problem of low protein content. Based on over-compensation strategy, a new concentration-shift method was proposed to cultivate heterotrophic Chlorella vulgaris, aiming to increase protein content. With a prior starvation period, microalgae utilized more nitrate and accumulated more proteins compared to one-stage cultivation. Considering the convenience of operation, nitrate-added culture was adopted for producing heterotrophic microalgae, rather than sterile centrifugal culture. Operating parameters including nitrate concentration in N-deficient medium, N-starved time and nitrate concentration in N-rich medium were optimized, which were 0.18gl-1, 38h and 2.45gl-1, respectively. Under the optimized conditions, protein content in heterotrophic Chlorella reached 44.3%. Furthermore, the heterotrophic microalga was suggested to be a potential single-cell protein source according to the amino acid composition.
authors.affiliation: Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu 610065, China. Electronic address: xietonghui@scu.edu.cn.
authors.forename: Tonghui
authors.initials: T
authors.lastname: Xie
authors.affiliation: Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China. Electronic address: xiayun@cib.ac.cn.
authors.forename: Yun
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu 610065, China. Electronic address: 407369800@qq.com.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu 610065, China. Electronic address: 328036601@qq.com.
authors.forename: Xingrui
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu 610065, China. Electronic address: zhangyongkui@scu.edu.cn.
authors.forename: Yongkui
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D048408:Chlorella vulgaris / Q000378:metabolism*; D052836:Heterotrophic Processes; D008055:Lipids / Q000096:biosynthesis; D058086:Microalgae / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism
chemical_list: D008055:Lipids; D009566:Nitrates
keywords: Chlorella; Heterotrophic microalgae; Nitrogen starvation; Over-compensation; Protein