Wageningen University, the Netherlands.
Biotechnol Prog. 2009 Sep-Oct;25(5):1343-52. doi: 10.1002/btpr.196.
In this work, the dependency of the volumetric hydrogen production rate of ammonium-limited Rhodobacter capsulatus chemostat cultures on their imposed biomass concentration and dilution rate was investigated. A deceleration-stat experiment was performed by lowering the dilution rate from 1.0 d(-1) to zero aimed at a constant biomass concentration of 4.0 g L(-1) at constant incident light intensity. The results displayed a maximal volumetric hydrogen production rate of 0.6 mmol m(-3) s(-1), well below model predictions. Possibly the high cell density limited the average light availability, resulting in a sub-optimal specific hydrogen production rate. To investigate this hypothesis, a gradient-stat experiment was conducted at constant dilution rate of 0.4 d(-1) at constant incident light intensity. The biomass concentration was increased from 0.7 to 4.0 g L(-1) by increasing the influent ammonium concentration. Up to a biomass concentration of 1.5 g L(-1), the volumetric hydrogen production rate of the system increased according to model predictions, after which it started to decline. The results obtained provide strong evidence that the observed decline in volumetric hydrogen production rate at higher biomass concentrations was at least partly caused by a decrease in light availability.
在这项工作中，研究了铵限制的荚膜红细菌恒化器培养物的体积产氢率对其强制生物量浓度和稀释率的依赖性。通过将稀释率从 1.0 d(-1)降低到零，进行了减速实验，目的是在恒定入射光强度下将生物量浓度保持在 4.0 g L(-1)。结果显示，最大体积产氢率为 0.6 mmol m(-3) s(-1)，远低于模型预测。高细胞密度可能限制了平均光可用性，导致最佳比产氢率降低。为了验证这一假设，在恒定入射光强度下，以恒定稀释率 0.4 d(-1)进行了梯度实验。通过增加入口铵浓度，将生物量浓度从 0.7 增加到 4.0 g L(-1)。在生物量浓度达到 1.5 g L(-1)之前，根据模型预测，系统的体积产氢率增加，之后开始下降。所得结果提供了有力的证据，表明在较高生物量浓度下观察到的体积产氢率下降至少部分是由于光可用性降低所致。
