Alcoholic fermentation by yeast immobilized on maize stem disks filled with Ca-alginate

摘要

The bioethanol production from sugar beet thick juice using whole cells of Saccharomyces cerevisiae immobilized by two new combined strategies of yeast natural adhesion onto the maize stem ground tissue (MSGT) disks and Ca-alginate entrapment was examined in order to improve process efficiency through use of mechanically resistant and physically stable biocatalyst. The first strategy involves the development of immobilized biocatalyst in the form of MSGT discs overlaid with Ca- alginate (IB), while in the second strategy the MSGT discs were filled with Ca-alginate (IB?). The IB, was physically unstable and inconvenient for repeated batch or continuous processes. In contrast, the IB, showed high mechanical strength, high cells retention and fermentative activity during four successive cycles without any significant decrease in ethanol production. The average ethanol concentration, productivity and yield during repeated fermentation of sugar beet thick juice (initial sugar of 150 g/l) by IB were 69.18 g/l, 1.44 g/lh and 0.473 g/g (92.6% of the theoretical), respectively. The repeated batch fermentation by IB> is useful for reducing the cost of bio-ethanol production due to the savings in time and energy for inoculum preparation, easier ethanol recovery, and lower need for the utilization of costly centrifuges for yeast separation.