Sugars microbial degradation

Acarbose and Miglitol These agents are specific inhibitors of intestinal glucosidases and reduce the conversion of sucrose and starch to glucose. Their main effect is a delay, not a complete inhibition, of the absorption of carbohydrates. Postprandial blood sugar excursions are effectively reduced. Because a small portion of the carbohydrates enters the colon, their microbial degradation frequently causes flatulence or... 

During fermentation, the betacyanins turned out to be more stable than the betaxanthins, which is assumed to be due to their thermal stability rather than different tendencies of pigments toward microbial degradation. Besides these biological tools, beet extracts may also be purified by column chromatographic techniques. After removal of sugars, salts, and phenolics, the nature-derived color preparation will, however, require E number labeling. ... 

The example of a total extract composition of a tropical soil from the Amazon, Brazil, shows mycose as the major compound, numerous other monosaccharides, lipid components such as fatty acids and fatty alcohols, and natural product biomarkers (Fig. 9a). The mycose and elevated levels of the other saccharides reflect the efficient fungal/microbial degradation of plant detritus in the tropics. This can be compared to the saccharides in the soil from an almond orchard in California, where glucose and mycose are the main sugars with lipids, sterols and triterpenoids (Fig. 9b, ). 

There are also structural differences between humic substances or UDOM collected from rivers and oceans (Table I). Humic substances and UDOM from rivers are enriched in aromatic components compared with their counterparts from the ocean. Terrestrial vegetation is relatively rich in aromatic components, such as lignins and tannins, and this is reflected in the greater aromatic nature of DOM in rivers. These biopolymers are relatively resistant to microbial degradation and are important components of river DOM. Humic substances and UDOM from the ocean are enriched in carbohydrates compared with their counterparts from rivers. This is consistent with observations of higher C-normalized yields of neutral sugars in bulk DOM from the ocean compared with rivers (Table I). 

In contrast to the selective preservation theory, the condensation pathway proposes that humic substances are derived from the polymerization and condensation of low-molecular-weight molecules that are products of the partial microbial degradation of organic residues (Kogel-Knabner, 1993). Under this scheme of increasing complexa-tion, fulvic acids would be the first humic substances synthesized, followed by humic acids and then humin (Stevenson, 1994). The two commonly accepted condensation models are the polyphenol theory and the sugar-amine or mela-noidin theory. 

By examination of the recent literature as reviewed by Tissot and Welte (1978), one gets the impression that the diagenesis of humic substances to form kerogen is well understood. In effect, many consider kerogen to be formed via condensation mechanisms in which aquatic plant substances are microbially degraded to form soluble monomers that condense to form humic polymers that eventually condense to form kerogen. The melanoidin pathway (sugar-amino acid condensation products) has been invoked by some to explain the structures formed (Nissenbaum and Kaplan, 1972 Hue and Durand, 1973, 1977 Welte, 1973 Nissenbaum, 1974 Stuermer et al. 1978 Tissot and Welte, 1978). 

Bagasse utilization is of prime interest to the sugar industry. Microbial degradation has been researched for many years. However, in this time of ever increasing fuel costs, bagasse remains the prime fuel in most raw cane sugar factories. In addition, bagasse also is used to make paper board. New process developments have lowered the minimum size of plant to produce paper economically. 

Humic material does not appear to be a prominent component of this HMW fraction. The principal components appear to be proteins and sugars, particularly N-acetylamino sugars, which probably originate from the degradation of microbial cell walls. 

To be able to study cellulose (Solka-floc) degradation without microbial conversion of the sugars formed, separate hydrolysis experiments were carried out in stirred flasks without cells. The conditions in these experiments were the same as during the corresponding fermentation... 

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