ABSTRACT
Liquid extraction is one means of removing metabolic products continuously during a fermentation and so reducing product inhibition. It is known that microbial organisms are attracted to liquid-liquid interfaces, and it is important for the design of extraction systems to establish if this has a detrimental effect on the rate of extraction. The extraction of ethanol from aqueous suspensions of yeast (Saccharomyces cerevisiae) using n- decanol is described in this paper. It was found that the presence of the yeast cells severely reduced the rate of ethanol extraction. The overall mass transfer coefficient was reduced from 5.0 x 10(-6) to 0.7 x 10(-6) m/s. This reduced overall mass transfer coefficient was unaffected by yeast concentration in the range 0.1-20 kg/m(3). The results are consistent with the yeast cells adsorbing to the interface in closely packed layers and preventing mass transfer by simply reducing the available interfacial area. Optical microscope observations confirmed that a yeast layer several cell diameters thick rapidly built up at the interface when a small decanol droplet was added to a yeast suspension.
ABSTRACT
A detailed study of a method for solasodine analysis has been carried out and the suitability of chemical analysis for solasodine determination in plant material evaluated. A number of problems with the analytical isolation of solasodine and its subsequent colorimetric determination have been highlighted: oven drying of plant material greater than 100 degrees leads to solasodine loss; cell disruption of the dry plant material is required if complete and rapid extraction of solasodine is to take place; hydrolysis of plant extract residues in greater than 1 N acid leads to solasodine loss; the colorimetric procedure is more temperamental than past methods have indicated, especially with regard to the specificity of the reaction and the instability of the complex.
