Fuels, Chemical and Metals from Bioprocesses

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F E R M E N T A T I O N P R O C E S S F O R T H E P R O D U C T I O N O F

P O L Y S A C C H A R I D E S

Geoffrey T Banks, Paul D Browning, Horsham, United Kingdom assigned to Imperial Bio- technology Limited

Polysaccharides, such as xanthan gum, are pro- duced by culturing microorganisms, e.g. of the Xanthomonas genus, in a two stage process. In the first stage, growth of the microorganism is favored, e.g. by using a predetermined quantity of a carbon-containing nutrient which does not support biosynthesis of the polysaccharide. In the second stage, the conditions are such that biosynthesis of the polysaccharide takes place with substantially no growth of the micro- organism, e.g. by adding carbohydrate in the absence of nutrient required for polysaccharide growth. By this process, the requirement for oxy- gen is greatly reduced at the time when the cul- ture medium has its highest viscosity, thereby minimizing problems of low oxygen transfer capability in viscous media.

T W O P H A S E A N A E R O B I C D I G E S T I O N

Sambhunat Ghosh, David Chynoweth, Paul Tarman assigned to Institute of Gas Technology

A two phase anaerobic digestion process for production of methane from organic car- bonaceous material in which an active acid for- ming microbial population is maintained in a first acid forming digestion phase and an active methane forming microbial population is main- tained in a second methane forming digestion phase, the liquid effluent from the acid forming digestion phase being passed to a first methane forming digester and gaseous product from the acid forming digestion phase being passed to a second separated methane forming digester for production of methane in the first and second methane forming digesters of the methane for- ming digestion phase. The two separated methane digestion phases provide increased overall methane production.

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