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Dark fermentative bioethanol production process yields carbon dioxide (CO 2 ) and organic acids as by-products. The so-yielded CO 2 is a nearly saturated gas of high CO 2 purity, which is commonly utilized in food industries as supplements. The potential utilization pathways for the CO 2 generated and released from the ethanol fermentation process (denoted as “fermentation CO 2 ”) include production of biofuels by CO 2 fixation of microalgae and succinic acid fermentation by non-photosynthetic microorganisms. This study compared the performances of these two CO 2 fixing pathways using Chlorella vulgaris or Actinobacillus succinogenes cultures. The highest carbon fixation rate achieved by Actinobacillus succinogenes was 388.8 g/L-d in 2-L reactor, which is about 188 times to that by Chlorella vulgaris (2.06 g/L-d) in the reactor at the same volume. This study ultimately demonstrated the advantages of adopting succinic acid production process compared to those frequently addressed in literature using microalgae-based biofuels. [ABSTRACT FROM AUTHOR]

Concentration of ethanol from the fermentation broth is an energy-intensive process. Very high gravity (VHG) process with modified polyvinyl alcohol-immobilized Zymomonas mobilis cells integrated with in situ bioethanol removal via vacuum membrane distillation (VMD) was proposed to mitigate product inhibition effects in VHG fermentation. The proposed VHG + VMD system, at 300 g/L glucose loading, produced 127.4 g/L (16.1% v/v) ethanol, at 63.7 g/L−h productivity and 84.9% glucose conversion rate, which is the highest in reported literature. [ABSTRACT FROM AUTHOR]