Heterotrophic cultivation of Chlorella has achieved commercial success, but the application of Chlorella biomass is still limited due to the high cost of biomass production. In this study, an effective and industrially scalable heterotrphic cultivation technology has been developed for a production strain Chlorella sorokiniana GT-1. Under the optimized culturing conditions, the ultrahigh biomass concentration of 271 and 247 g L⁻¹ was achieved in 7.5 L bench-scale and 1000 L pilot-scale fermenters, respectively. Technoeconomic (TE) analysis indicated that the production cost of C. sorokiniana GT-1 could be reduced to $1601.27 per ton of biomass if the biomass concentration reached 200 g L⁻¹, which is 24.2% lower than that of the reported highest Chlorella biomass production through fermentation with the same TE model. Under the same growth conditions, the maximum biomass concentration of a low-starch mutant SLM2 was reduced to 93 g L⁻¹, which was 54% lower than that of the wild type, indicating the capabilities of C. sorokiniana GT-1 cells in accumulating large amounts of starch are essential for achieving the ultrahigh-cell-density under the heterotrophic conditions. In addition, the ultrahigh-cell-density growth potential of C. sorokiniana GT-1 cells was inferred to be related to the intrinsic biological characteristics including the tolerance to low dissolved oxygen and a moderate doubling time under the heterotrophic conditions as well. The breakthrough in cultivation technology is promising for Chlorella industry and would expand its applications in food and feed.

中文翻译：

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单细胞绿藻 Chlorella sorokiniana 的超高细胞密度异养培养用于生物质生产

小球藻的异养栽培已取得商业成功，但由于生物质生产成本高，小球藻生物质的应用仍受到限制。在这项研究中，已经为生产菌株Chlorella sorokiniana GT-1 开发了一种有效且工业上可扩展的异养培养技术。在优化的培养条件下，在 7.5 L 小试规模和 1000 L 中试规模发酵罐中分别实现了271 和 247 g L ^{-1的超高生物量浓度。}技术经济（TE）分析表明，如果生物质浓度达到200 g L ^{-1 ，} C. sorokiniana GT-1的生产成本可降低至每吨生物质1601.27美元。，这比报道的使用相同 TE 模型通过发酵产生的最高小球藻生物量低 24.2%。在相同生长条件下，低淀粉突变体SLM2的最大生物量浓度降至93 g L ^-1，比野生型低54%，表明C. sorokiniana GT-1细胞在积累大量淀粉对于在异养条件下实现超高细胞密度至关重要。此外，C. sorokiniana的超高细胞密度生长潜力推测GT-1细胞与内在生物学特性有关，包括对低溶解氧的耐受性和异养条件下的适度倍增时间。栽培技术的突破为小球藻产业带来了希望，并将扩大其在食品和饲料中的应用。