Liu Tingting, Liu Fei, Wang Chao, Wang Zhenyao, Li Yuqin
School of Chemical Engineering, Xiangtan University, Xiangtan, 411105, People's Republic of China.
World J Microbiol Biotechnol. 2016 Dec;32(12):202. doi: 10.1007/s11274-016-2164-7. Epub 2016 Oct 31.
A model of heterotrophy and nutrition-limitation transition cultivation for efficient algal biomass and lipid production was proposed in this study, wherein sufficient robust heterotrophic-seed cells submitted into nitrogen-starvation induction for boosted lipid accumulation. The results demonstrated that heterotrophic-seed (HS) achieved specific growth rate of 1.35 day and biomass productivity of 1.93 mg/L/d, representing 6.42- and 32.16-fold, 2.01- and 2.75-fold more than that of photoautotrophic-seed (PS) and mixtrophic-seed (MS). Even though subsequent nutrition-limitation cultivation repressed the growth of HS, the overall lipid productivity caused by nitrogen-starvation was not offset by biomass loss. The most favorable lipid productivity (465.61 mg/L/d) of HS was 3.25 and 52.31 times higher than that of MS and PS. The high content of monounsaturated fatty acids (50.13%) over saturated and polyunsaturated fatty acids (totally 47.39%) in HS cells could provide superior oxidation stability and lower viscosity for biofuels generated from algal biomass feedstock. These findings suggested the feasibility of using heterotrophy and nutrition-limitation transition cultivation for enhancing the overall lipid productivity. Further, several critical enzymes (i.e. G3PDH, ME, and ACAD) were highly related to lipid accumulation and showed especially pronounced up-regulation or down-regulation expression in HS, which provide indications for shedding light on the molecular mechanisms of lipid accumulation and a prospective metabolic engineering for lipid production.
本研究提出了一种用于高效生产藻类生物质和脂质的异养与营养限制过渡培养模型，其中将足够健壮的异养种子细胞进行氮饥饿诱导以促进脂质积累。结果表明，异养种子（HS）的比生长速率为1.35天，生物质生产力为1.93毫克/升/天，分别比光自养种子（PS）和兼养种子（MS）高6.42倍和32.16倍、2.01倍和2.75倍。尽管随后的营养限制培养抑制了HS的生长，但氮饥饿导致的总体脂质生产力并未因生物质损失而抵消。HS最有利的脂质生产力（465.61毫克/升/天）分别比MS和PS高3.25倍和52.31倍。HS细胞中高含量的单不饱和脂肪酸（50.13%）超过饱和脂肪酸和多不饱和脂肪酸（总计47.39%），可为由藻类生物质原料生产的生物燃料提供卓越的氧化稳定性和更低的粘度。这些发现表明利用异养与营养限制过渡培养提高总体脂质生产力的可行性。此外，几种关键酶（即G3PDH、ME和ACAD）与脂质积累高度相关，并在HS中表现出特别明显的上调或下调表达，这为阐明脂质积累的分子机制和脂质生产的前瞻性代谢工程提供了线索。
