Set-Up and Validation of a Dynamic Solid/Gas Bioreactor

• Main Author: Lloyd-Randol, Jennifer D.
• Format: Text
• Language: unknown
• Published: KAUST Research Repository 2012
• Subjects: Antarc*; Antarctica
• Online Access: https://dx.doi.org/10.25781/kaust-d8a6y; https://repository.kaust.edu.sa/handle/10754/224713

The limited availability of fossil resourses mandates the development of new energy vectors, which is one of the Grand Challenges of the 21st Century [1]. Biocatalytic energy conversion is a promising solution to meet the increased energy demand of industrialized societies. Applications of biocatalysis in the gas-phase are so far limited to production of fine chemicals and pharmaceuticals. However, this technology has the potential for large scale biocatalytic applications [2], e.g. for the formation of novel energy carriers. The so-called solid/gas biocatalysis is defined as the application of a biocatalyst immobilized on solid-phase support acting on gaseous substrates [3]. This process combines the advantages of bio-catalysis (green chemistry, mild reaction conditions, high specicity & selectivity) and heterogeneous dynamic gas-phase processes (low diffusion limitation, high conversion, simple scale-up). This work presents the modifications of a PID Microactivity Reference reactor in order to make it suitable for solid/gas biocatalysis. The reactor design requirements are based on previously published laboratory scale solid/gas systems with a feed of saturated vapors [4]. These vapors are produced in saturation flasks, which were designed and optimized during this project. Other modifications included relocation of the gas mixing chamber, redesigning the location and heating mechanism for the reactor tube, and heating of the outlet gas line. The modified reactor system was verified based on the Candida antarctica lipase B catalyzed transesterication of ethyl acetate with 1-hexanol to hexyl acetate and ethanol and results were compared to liquid-phase model reactions. Products were analyzed on line by a gas chromatograph with a flame ionization detector. C. antarc- tica physisorbed on silica particles produced a 50% conversion of hexanol at 40 C in the gas-phase. A commercial immobilized lipase from Iris Biotech produced 99% and 97% conversions of hexanol in similar experiments. This project achieved its goal to design, establish and successfully verify a solid/- gas biocatalysis reactor. Future work will target optimization of the reactor's operating conditions and the development of whole cell catalysts for energy production reactions. Potential experiments include the study of hydrogenolytic carbon dioxide reduction to methanol by free enzymes or methanogenic organisms [5], and the investigation of hydrogen production by water splitting of algae or cyanobacteria.