Starch catalytic conversion

Hydrolysis. The chemical reaction of a substance with water to form one or more new substances. Examples of hydrolysis are the catalytic conversion of starch into glucose the catalytic or enzymatic conversion of sucrose into glucose and fructose the conversion of natural fats into fatty acids and glycerin... 

As discussed above, glucoamylases consist of three domains a catalytic domain a linker domain and a starch-binding domain. These domains can be in different orders in which the catalytic domain is located at the N-terminus or the C-terminus and conversely the starch-binding domain is at the C-terminus or the N-terminus, with the linker domain between the two. 

Renewable raw materials can contribute to the sustainability of chemical products in two ways (i) by developing greener, biomass-derived products which replace existing oil-based products, e.g. a biodegradable plastic, and (ii) greener processes for the manufacture of existing chemicals from biomass instead of from fossil feedstocks. These conversion processes should, of course, be catalytic in order to maximize atom efficiencies and minimize waste (E factors) but they could be chemo- or biocatalytic, e.g. fermentation [3-5]. Even the chemocatalysts themselves can be derived from biomass, e.g. expanded com starches modified with surface S03H or amine moieties can be used as recyclable solid acid or base catalysts, respectively [6]. 

An efficient single-step catalytic process was recently developed for the conversion of glucan-type polysaccharides, especially starch, to sorbitol [15]. This process is characterized by the simultaneous hydrolysis of the polysaccharide and hydrogenation of the liberated monosaccharide. The catalyst used is Ru-loaded H-USY zeolite (3 % wlw Ru) in which the zeolitic material fulfils the role of metal carrier (Ru) and solid-acid catalyst. The zeolite provides the Brpnsted acidity required for the hydrolysis reaction either because of its outer surface or by introducing some homogeneous acidity, and the Ru catalyzes the hydrogenation of D-glucose to sorbitol (Scheme 2). 

The catalytic effect of the hydroxide ion would normally be represented as part of the reaction rate constant (k ) for each temperature, because catalyst concentration normally remains constant. However, in the case of alkaline degradation of starch or cellulose, organic acids are produced which are converted to their salts by the alkali present, thus reducing the hydroxide ion concentration. Therefore, it seemed that this degradation reaction could be represented by second-order kinetics, with the hydroxide ion concentration determined by the stoichiometry of conversion of starch or cellulose to organic acids. 

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