ISCF WAVE 1 IB: Process intensification of cellulosic biofuel production using continuous product extraction with microbubble technology

本项目的主要目标是研究在60-65℃下运行的发酵反应器中微泡的连续提取能力，以提高纤维素生物燃料的产量。糖类发酵生产酒精的主要问题之一是，由于产品对生产微生物的抑制作用，发酵生物在高产品浓度下的性能下降。对于在相对较高的温度(50-70摄氏度)下生长的嗜热菌来说，情况尤其如此。然而，其中一些细菌特别适合在可再生的木质纤维原料上生长，因此不断从发酵液中去除酒精的有效方法将使木质纤维素制乙醇的过程更加经济。在以前的研究中，我们已经证明，在高气体流过速率下，使用正常大小(Mm)的气泡，乙醇可以连续从发酵液中剥离，从而消除其抑制作用。然而，所需的气体流速太高，不切实际。当使用气体从液体中剥离物质，或将物质(如氧气)从气体中输送到液体中时，确定传质速率的最重要的特征是气泡表面积与体积的比率。对于相同体积的气体，较小的气泡比较大的气泡具有更大的表面积，因此应该更有效地从溶液中剥离乙醇。然而，较小的气泡可能对细菌造成更大的破坏，因此不能假定它们的整体好处。在这个项目中，我们将开发设备，允许在小型生物反应器中连续产生和提取微泡，在含有乙醇但没有细胞的模拟混合物中展示其有效性，并最终研究其从含有60-65℃生长的细菌的发酵中连续提取乙醇的有效性。将监测对细菌的影响，并修改条件(温度、气泡大小等)以实现最佳性能。

The main objective of this project is to investigate the continuous extraction capabilities of microbubbles in a fermentation reactor operated at 60-65C, to improve cellulosic biofuel production. One of the main issues pertaining to fermentation of sugars to alcohol is the decline in performance of fermentative organisms at high product concentrations, due to the inhibitory effects of the product on the producing organism. This is particularly true with thermophilic bacteria which grow at relatively high temperatures (50-70C). However, some of these bacteria are particularly well suited to growth on renewable, lignocellulosic feedstocks, so an effective way to continuously remove the alcohol from the fermentation broth would make the lignocellulose to ethanol process more economic. In previous studies we have already shown that at high gas flow through rates, using normal (mm) sized bubbles, ethanol can be continuously stripped from the fermentation broth, so removing its inhibitory effects. However, the gas flow rates required are far too high to be practical. When using a gas to strip material from a liquid, or to deliver material (eg oxygen) from a gas to a liquid the most important feature for determining the mass transfer rate is the ratio of bubble surface area to volume. For the same volume of gas, smaller bubbles will have a higher surface area than larger bubbles and should therefore be more effective at stripping ethanol from a solution. However, smaller bubbles could potentially be more damaging to the bacteria, so their overall benefits cannot be assumed. In this project we will develop devices to allow continuous microbubble generation and extraction in a small scale bioreactor, demonstrate its effectiveness in simulated mixtures containing ethanol but no cells and finally investigate its effectiveness for continuous ethanol extraction from fermentations containing bacteria growing at 60-65C. The effects on the bacteria will be monitored and conditions (temperature, bubble size etc) modified to achieve optimal performance.