Introduction<\/h3>\n\n\n\n
Starch is an essential food ingredient and energy source to meet humans\u2019 nutritional requirements1<\/a><\/sup>. The annual global demand for starch is above 120\u2009million tons and is projected to grow at a compound annual growth rate of 4\u20135% as a result of population growth, consumption upgrading, as well as increasing starch demand in industrial applications2<\/a>,3<\/a><\/sup>. Starch supply through the current production mode, traditional agriculture\/crop cultivation, can barely meet the dramatically growing demand due to (i) the limited arable land4<\/a>,5<\/a><\/sup>, (ii) the rate constraint of natural photosynthesis-based carbon fixation6<\/a><\/sup>, and (iii) the threat of climate change such as CO2<\/sub> emission and global warming7<\/a><\/sup>.<\/p>\n\n\n\n CO2<\/sub>-to-starch conversion through low-carbon biomanufacturing is a possible approach to address the challenges and reshape a carbon-negative food supply route via cellular agriculture8<\/a>,9<\/a><\/sup>. With the consumption of renewable electricity, CO2<\/sub> was electro-catalyzed to liquid energy-rich C1\/C2 chemicals, such as formate and acetate10<\/a><\/sup>. These short-chain substrates are then transformed into more complex compounds by enzymatic catalysis11<\/a><\/sup> or microbial transformation12<\/a>,13<\/a><\/sup>. The whole process enables an energy efficiency four-fold higher than natural photosynthesis, representing an energy-efficient approach for food ingredient production14<\/a><\/sup>.<\/p>\n\n\n\n In the past several years, there have been continuous breakthroughs in CO2<\/sub> electro-conversion to ensure the production of pure acetate at a CO2<\/sub> fixation rate dramatically higher than natural photosynthesis12<\/a>,15<\/a><\/sup>. The subsequent conversion of acetate to starch, however, demands microbes capable of synthesizing and accumulating starch at a superior-to-nature rate and content. The food-safe yeast Yarrowia lipolytica<\/em> strain16<\/a><\/sup>, which could naturally assimilate acetate17<\/a><\/sup> and produce a variety of health-relevant molecules at high levels18<\/a>,19<\/a>,20<\/a><\/sup>, is an excellent chassis strain to develop as an efficient producer of starch-rich micro-grain.<\/p>\n\n\n\n Herein, we reconfigure the oleaginous yeast to an efficient workhouse for starch biosynthesis by rewiring the starch biosynthesis and gluconeogenesis pathways, and regulating cell morphology (Fig. 1<\/a>). The engineered strains lay the foundation to understand the natural and remodeled machinery for starch biosynthesis, and facilitate a superior-to-nature high-level production of starch with customized composition.<\/p>\n\n\n
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