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29. Turning the industrially relevant marine alga Nannochloropsis red: one move for multifaceted benefits.

Author

Liu, Meijing, Yu, Lihua, Zheng, Jie, Shao, Shengxi, Pan, Yufang, Hu, Hanhua, Shen, Lili, Wang, Wenda, Zhou, Wenguang, and Liu, Jin

Subjects
*UNSATURATED fatty acids, *EICOSAPENTAENOIC acid, *BIOTECHNOLOGY, *ASTAXANTHIN, *HYDROXYLASES, *MICROALGAE
Abstract

Summary Nannochloropsis oceanica is an industrially relevant marine microalga rich in eicosapentaenoic acid (EPA, a valuable ω‐3 polyunsaturated fatty acid), yet the algal production potential remains to be unlocked. Here we engineered N. oceanica to synthesize the high‐value carotenoid astaxanthin independent of high‐light (HL) induction for achieving multifaceted benefits. By screening β‐carotenoid ketolases and hydroxylases of various origins, and strategically manipulating compartmentalization, fusion patterns, and linkers of the enzyme pair, a remarkable 133‐fold increase in astaxanthin content was achieved in N. oceanica. Iterative metabolic engineering efforts led to further increases in astaxanthin synthesis up to 7.3 mg g−1, the highest reported for microalgae under nonstress conditions. Astaxanthin was found in the photosystem components and allowed the alga HL resistance and augmented EPA production. Besides, we achieved co‐production of astaxanthin and EPA by the engineered alga through a fed‐batch cultivation approach. Our findings unveil the untapped potential of N. oceanica as a robust, light‐driven chassis for constitutive astaxanthin synthesis and provide feasible strategies for the concurrent production of multiple high‐value biochemicals from CO2, thereby paving the way for sustainable biotechnological applications of this alga. [ABSTRACT FROM AUTHOR]

Published
2024
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44. Study on Constitutive Model of Cyclic Elastoplastic Behavior of 6082-T6 Aluminum Alloy.

Author

Wu, Mingze, Fan, Shenggang, Zhou, Hang, Dong, Daoyang, Liu, Meijing, and Sun, Zekang

Subjects
ALUMINUM alloys, MECHANICAL behavior of materials, ELASTOPLASTICITY, STRAINS & stresses (Mechanics), YIELD surfaces, CYCLIC loads
Abstract

This paper aims to propose an improved constitutive model based on the classical Chaboche mixed hardening model to describe the cyclic elastoplastic behavior of 6082-T6 aluminum alloy. First, 16 specimens from 6082-T6 aluminum alloy were tested under monotonic and cyclic loads. The variation law of the backstress, yield surface size, elastic modulus, and peak stress with equivalent plastic strain was obtained and analyzed. The results show that the kinematic hardening before and after the load reversal had a significant difference. Meanwhile, the elastic modulus and yield surface radius experienced a rapid decay at the early stage of equivalent plastic strain growth and then tended to flatten out. Based on these phenomena, a modified constitutive model based on the classical Chaboche mixed hardening model was proposed. The evolutions of isotropic hardening/softening, backstress, and elastic modulus were introduced. Then, the model was introduced to the ABAQUS software by the user subroutine to define a material's mechanical behavior (UMAT) subroutine and corresponding parameters were provided. Finally, the proposed constitutive model was proven to capture the cyclic elastoplastic properties of 6082-T6 aluminum alloy well and had a significant improvement on the classical Chaboche mixed hardening model. Among them, the constitutive model can accurately describe the initial yield surface of 6082-T6, with an accuracy improvement of 26.6% compared to the Chaboche mixed hardening model, and an accuracy improvement of 7.44% in describing changes in elastic modulus. [ABSTRACT FROM AUTHOR]

Published
2024
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