Institute of Plankton Eco-Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo, 192-8577, Japan.
Laboratory of Restoration Ecology, Graduate School of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo, 192-8577, Japan.
Bioprocess Biosyst Eng. 2021 Aug;44(8):1659-1669. doi: 10.1007/s00449-021-02548-0. Epub 2021 May 21.
Anaerobic digestion is a mature technology; however, the mechanism of cell proliferation during starvation has not yet been clarified. In this study, a continuous stirred tank reactor (CSTR) treating food waste was exposed to deliberate starvation for 12 days. The cell density and the variability of digestate characteristics during starvation were monitored. Starvation increased cell density from 2.8 × 10 to 7.9 × 10 cells mL within 2 days and reduced the residual substrate. This increase in cell density was suggested owing to a switch of the anaerobic digester microorganisms' substrate preference to the complex fractions because the easily digestible fractions were exhausted. The prolonged starvation of more than approximately 3-6 days induced an increase in the free ammonia concentration to an inhibitive level of more than 0.10 g-N L for anaerobic digestion microorganisms due to the excessive ammonification of residual nitrogen, thereby resulting in a drastic decrease in cell density. Our results demonstrated that a deliberate starvation operation in an appropriate timeframe applied to a CSTR treating food waste is beneficial to proliferate cells and, at the same time, reduce residual substrate.
厌氧消化是一种成熟的技术；然而，细胞在饥饿状态下增殖的机制尚未阐明。本研究采用连续搅拌釜式反应器（CSTR）处理食物垃圾，故意让其饥饿 12 天。监测了饥饿期间细胞密度和消化物特性的变化。饥饿在 2 天内将细胞密度从 2.8×10增加到 7.9×10 个细胞/mL，并减少了残留底物。这种细胞密度的增加是由于厌氧消化微生物对复杂部分的底物偏好发生了变化，因为易消化部分已经耗尽。由于剩余氮的过度氨化，超过大约 3-6 天的长时间饥饿会导致游离氨浓度增加到抑制水平（超过 0.10 g-N L），从而抑制厌氧消化微生物，导致细胞密度急剧下降。我们的结果表明，在适当的时间内对处理食物垃圾的 CSTR 进行故意饥饿操作有利于细胞增殖，同时减少残留底物。
