Hussain Amir, Kangwa Martin, Abo-Elwafa Ahmed Gad, Fernandez-Lahore Marcelo
Downstream Bioprocessing Laboratory, School of Engineering and Science, Jacobs University, Campus Ring 1, 28759 Bremen, Germany.
Department of Biotechnology, Faculty of Agriculture, Al-Azhar University, Naser City, Cairo, 11884 Egypt.
AMB Express. 2015 May 1;5:25. doi: 10.1186/s13568-015-0111-x. eCollection 2015.
The influence of mass transfer on productivity as well as the performance of packed bed bioreactor was determined by varying a number of parameters; flow rate, glucose concentration and polymers (chitosan). Saccharomyces cerevisiae cells were immobilized in chitosan and non-chitosan coated alginate beads to demonstrate the effect on external mass transfer by substrate consumption time, lag phase and ethanol production. The results indicate that coating has a significant effect on the lag phase duration, being 30-40 min higher than non-coated beads. After lag phase, no significant change was observed in both types of beads on consumption of glucose with the same flow rate. It was observed that by increasing flow rates; lag phase and glucose consumption time decreased. The reason is due to the reduction of external mass transfer as a result of increase in flow rate as glucose is easily transported to and from the beads surface by diffusion. It is observed that chitosan acts as barrier for transfer of substrate and products, in and out of beads, at initial time of fermentation as it shows longer lag phase for chitosan coated beads than non-coated. Glucose consumption at low flow rate was lower as compared to higher flow rates. The optimum combination of parameters consisting of higher flow rates 30-90 ml/min and between 10 and 20 g/l of glucose was found for maximum production of ethanol.
通过改变多个参数（流速、葡萄糖浓度和聚合物（壳聚糖））来确定传质对填充床生物反应器生产率和性能的影响。将酿酒酵母细胞固定在壳聚糖和未涂覆壳聚糖的海藻酸盐珠粒中，以通过底物消耗时间、延迟期和乙醇产量来证明对外部传质的影响。结果表明，包衣对延迟期持续时间有显著影响，比未包衣的珠粒长30 - 40分钟。在延迟期之后，对于相同流速下葡萄糖的消耗，两种类型的珠粒均未观察到显著变化。观察到通过增加流速，延迟期和葡萄糖消耗时间会减少。原因是由于流速增加导致外部传质减少，因为葡萄糖通过扩散可以很容易地在珠粒表面进出。观察到在发酵初期，壳聚糖对底物和产物进出珠粒起到了屏障作用，因为与未包衣的珠粒相比，壳聚糖包衣的珠粒显示出更长的延迟期。与较高流速相比，低流速下的葡萄糖消耗较低。发现由30 - 90毫升/分钟的较高流速和10至20克/升的葡萄糖组成的参数最佳组合可实现乙醇的最大产量。
