Carbohydrate Upgrading

FIGURE 9.3 Hypothesized lignin structure and monomer units [23]. 

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Pyrolysis has a long history in the upgrading of biomass. The dry distillation of hardwood was applied in the early 1990s to produce organic intermediates (methanol and acetic acid), charcoal and fuel gas [3]. Today s processes can be tuned to form char, oil and/or gas, all depending on the temperature and reaction time, from 300 °C and hours, to 400-500 °C and seconds-minutes, to >700 °C and a fraction of a second [3, 19, 23, 24], The process is typically carried out under inert atmosphere. We illustrate the basic chemistry of pyrolysis by focusing on the conversion of the carbohydrate components (Fig. 2.4). The reaction of the lignin will not be covered here but should obviously be considered in a real process. Interested readers could consult the literature, e.g., [25]. Pyrolysis is discussed in more details elsewhere in this book [26],... 

Controlled degradation of chitosan, alginates and carrageenans — Upgrading and utilization of carbohydrates such as chitosan, sodium aiginate, carrageenan, cellulose,... 

Microbial cell-wall-lytic enzymes are widely used in the laboratory for cell breakage, proto-plasting of yeasts and bacteria, and for studies of the structure and composition of microbial cell walls (J ). Recently lytic systems have come under consideration as a specific and chemically mild way to rupture microbial cells on an industrial scale (2 ). There appear to be attractive commercial applications of lytic systems for the recovery of enzymes, antigens and other recombinant products accumulated within cells, for upgrading of microbial biomass for food and feed uses (4 5) and for the manufacture of functional biopolymers from cell wall carbohydrates (6). 

In the UK and the USA the product no longer really justifies itself as an animal feed. The set of conditions in which cheap methane could, through synthetic methanol, be economically converted to protein have now been replaced by others in which carbohydrates from agriculture are economic sources of ethanol, a fuel which directly rivals methanol. The value of the product might be upgraded if it were treated as a raw material from which a number of biological materials might be manufactured, and small-scale processes do exist for a few compounds which could be recovered from the cells. However, other constraints apply in the USSR where about 10 M tonnes of bacterial protein are produced each year from a variety of hydrocarbon feedstocks. ... 

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