Role of short-chain fatty acids in the hind gut.

Short-chain fatty acids (SCFA) are produced by microbial fermentation in the hindgut in considerable amounts. Most of the anions in hindgut contents are SCFA, mainly acetate, propionate and butyrate. SCFA are rapidly absorbed. Mechanisms involved in the transepithelial transport are discussed. Besides the contribution to the overall energy metabolism of animals or men, SCFA have a number of further important effects on the colonic mucosa. Factors affecting the pH of compartments in the mucosa, cell swelling, stimulation of mucin release and of mucosal blood flow are mentioned. Controversial reports are known on the role of SCFA in the metabolism of colonocytes. In spite of the conflicting opinions on the interaction between SCFA metabolism and the development of colitis ulcerosa, diverticulosis and colorectal cancer seems to exist. The obscure differences between the effects of SCFA on cell proliferation, differentiation and apoptosis of colonocytes in vivo and in vitro indicate that besides direct effects of SCFA systemic effects such as neural and humoral factors are of crucial importance. The opposing effects of SCFA on proliferation and apoptosis in normal colonocytes and in colonic cancer cells may open possibilities for prevention and/or therapy of patients with colonic diseases.

Determination of trehalose by flow injection analysis using immobilized trehalase.

A new method for the determination of trehalose by flow injection analysis (FIA) is described. The basic principle is the hydrolysis of the disaccharide trehalose into its monomer d-glucose by trehalase, a periplasmic enzyme of Escherichia coli. d-glucose is quantified spectrophotometrically after reaction with hexokinase and glucose-6-phosphate dehydrogenase. Trehalase is prepared by osmotic shock from a recombinant E. coli strain and precipitated with ammonium sulfate. The enzyme is immobilized on VA-Epoxy Biosynth from Riedel-de-Haën. The immobilization rate is about 60%. The FIA signals show a nonlinear dependence on the trehalose concentration. The resulting curve corresponds to a second-order polynomial that serves as a calibration function for test samples. Immobilized trehalase was used during a period of 4 months without any loss of suitability. Several samples of fermentation broth were tested. The results are verified by HPLC. Within an interval of 2 to 10 g/L trehalose the recovery is about 100-120% with a precision of 7% (coefficient of variation).