Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628 BC Delft, The Netherlands.
J Biotechnol. 2010 May 17;147(2):73-9. doi: 10.1016/j.jbiotec.2010.02.003. Epub 2010 Feb 13.
Mixed microbial cultures enriched in feast-famine sequencing batch reactors (SBRs) can accumulate large amounts of the bioplastic PHB under conditions of ammonium starvation. If waste streams are to be used as a substrate, nutrient starvation may not always be achievable. The aim of this study was to investigate the influence of ammonium on PHB production in the PHB production stage of the process. The biomass was enriched in an acetate-fed (carbon limited) feast-famine SBR operated at 30 degrees C, 1-d sludge residence time and with a cycle length of 12h. The biomass was used in three fed-batch experiments with medium C/N ratios of infinity (ammonium starvation), 40 Cmol Nmol(-1) (ammonium limitation) and 8 Cmol Nmol(-1) (ammonium excess) and acetate as the carbon source. Under conditions of ammonium starvation the biomass reached a maximum PHB content of 89 wt% after 7.6h, under ammonium limitation 77 wt% after 9.3h and under ammonium excess 69 wt% after 4.4h. PHB contents decreased after these maxima were reached. PHB production slowed down more with time with larger ammonium availability. Growth led to a dilution of the PHB pool after the maximum PHB content was reached. Nutrient starvation seems thus to be the best strategy for maximal PHB production.
在氨饥饿条件下，富含 feast-famine 序批式反应器（SBR）的混合微生物培养物可以积累大量的生物塑料 PHB。如果要使用废水作为底物，营养饥饿可能并不总是可行的。本研究旨在研究氨对该过程 PHB 生产阶段 PHB 生产的影响。在 30°C、1-d 污泥停留时间和 12h 周期长度下，采用乙酸喂养（碳限制）的 feast-famine SBR 富集生物质。生物质用于三个具有无限中 C/N 比（氨饥饿）、40 Cmol Nmol(-1)（氨限制）和 8 Cmol Nmol(-1)（氨过量）和乙酸作为碳源的分批补料实验。在氨饥饿条件下，生物质在 7.6h 后达到 89wt%的最大 PHB 含量，在氨限制条件下在 9.3h 后达到 77wt%，在氨过量条件下在 4.4h 后达到 69wt%。达到这些最大值后，PHB 含量下降。随着时间的推移，可用的氨越多，PHB 生产的速度就越慢。在达到最大 PHB 含量后，生长导致 PHB 池的稀释。因此，营养饥饿似乎是实现最大 PHB 产量的最佳策略。
