The hydrolysis of bile acid conjugates

Studies were made of a) the relationship of bile acid structure and analytical recoveries (measured by 3-hydroxysteroid oxidoreductase) following vigorous alkaline hydrolysis of bile acid conjugates and b) the relationship of structure and hydrolysis time of taurine- and glycine bile acid conjugates in a reaction catalyzed by glycocholic acid hydrolase. Alkaline hydrolysis resulted in good recoveries of hydroxy and 7 and 12- oxo-bile acids but poor recoveries of 3-oxo-bile acids. Borohydride reduction of the 3-oxo-acids prevented these losses. Complete enzymatic hydrolysis of glycine conjugated bile acids was about five times more rapid than that of taurine conjugates. Hydrolysis of conjugates containing oxo groups was slow. Borohydride reduction of oxoacids corrected this and did not inhibit enzymatic hydrolysis. It was concluded that both vigorous alkaline and enzymatic hydrolysis are satisfactory in bile acid assays if borohydride reduction is instituted before the hydrolytic step. However, due to the presence of possible enzyme inhibitors and solubility difficulties, strong alkaline hydrolysis is preferable to enzymatic hydrolysis in fecal bile acid determinations at this time.     

Enzyme-accelerated hydrolysis of polyglycolic acid.

In a preliminary study of the enzyme-polymer interactions, the role of 15 enzymes in the in vitro hydrolysis of polyglycolic acid has been investigated. Carboxypeptidase A, alpha-chymotrypsin, clostridiopeptidase A and ficin increase the rate of hydrolysis of this synthetic polymer, illustrating the ability of enzymes to influence polymer degradation.     

Preparation of low-molecular weight alginic acid by acid hydrolysis

Three kinds of low-molecular weight alginic acid fractions, Alg.A, B, and C, were prepared from a commercial alginic acid by acid hydrolysis using phosphoric acid. Alg.A was obtained as an insoluble fraction by the filtration of mixture. Alg.B was obtained as a precipitate by pouring the filtered solution into water. Alg.C was obtained as a precipitate by pouring the filtrate into methanol. Measurements with ¹³C NMR, GPC and WAXS were performed on the prepared fractions for characterization.

Alg.A was composed of rich M and G blocks, and had DP_n and DP_w/DP_n values of 79 and 3.11, respectively. Alg.B was mainly composed of M block, and had DP_n and DP_w/DP_n values of 38 and 2.57, respectively. Alg.C had a random structure including many alternating sequences, and had DP_n and DP_w/DP_n values of 35 and 2.11, respectively. Alginic acid oligomers prepared in this study, Alg.B and C, were improved regarding in solubility in water and the viscosity of their aqueous solution.     

Controlled acid hydrolysis of colominic acid under microwave irradiation

The hydrolysis of colominic acid under microwave irradiation was studied and compared with traditional heating methods. The microwave irradiation has several advantages over the heating method in the hydrolysis of colominic acid: (a) products with higher degrees of polymerization are obtained, (b) less lactone byproducts are observed, and (c) the hydrolytic rate is much faster. These advantages are probably due to the microwave effect. Oligosialic acids as the products of the acid hydrolysis of polysialic acid with conventional heating methods were fully lactonized, especially under the conditions of higher temperature and stronger acid.     

Partial acid hydrolysis of cellulosic materials as a pretreatment for enzymatic hydrolysis

Partial acid hydrolysis was studied as a per treatment to enhance enzymatic hydrolysis, such a pretreatment was carried out in a continuous flow reactor on oak corn Stover, newsprint, and Solka Floc at temperatures ranging from 160 to 220°C, acid concentration ranging from 0 to 1.2%, and a fixed treatment time of 0.22 min. The resulting slurries and solids were than hydrolyzed with Trichoderma ressei QM 9414 cellulase at 50°C for 48 hr. For all substrates except Solka Floc, increased glucose yields were achieved during enzymatic hydrolysis of the pretreated materials as compared to hydrolysis of the original substrate. In several cases, after pretreatment, 100° of the potential glucose content of the substrate was converted to glucose after 24hr of enzymatic hydrolysis. It is felt that the increased glucose yields achieved after this pretreatment are due to acid's removal of hemicellulose, reduced degree of polymerization, and possibly due to a change in the crystal structure of the cellulose.     

Kinetics of enzymic hydrolysis of malto-oligosaccharides: A comparison with acid hydrolysis

The hydrolysis of malto-oligosaccharides G₃-G₆ catalysed by porcine pancreatic alpha-amylase was investigated kinetically at 25°. Kinetic parameters corresponding to different positions of enzymic attack were determined and product inhibition was evaluated. The enzymic hydrolysis was compared in terms of reaction rate and pattern of action with hydrolysis in 0.1m H₂SO₄ at 70°. Mathematical models for the mechanism of hydrolysis were developed and a good rationalisation of the experimental results was achieved.     

Thermal synthesis and hydrolysis of polyglyceric acid

Polyglyceric acid was synthesized by thermal condensation of glyceric acid at 80° in the presence and absence of two mole percent of sulfuric acid catalyst. The acid catalyst accelerated the polymerization over 100-fold and made possible the synthesis of insoluble polymers of both L- and DL-glyceric acid by heating for less than 1 day. Racemization of L-glyceric acid yielded less than 1% D-glyceric acid in condensations carried out at 80°C with catalyst for 1 day and without catalyst for 12 days. The condensation of L-glyceric acid yielded an insoluble polymer much more readily than condensation of DL-glyceric acid. Studies of the hydrolysis of poly-DL-glyceric acid revealed that it was considerably more stable under mild acidic conditions compared to neutral pH. The relationship of this study to the origin of life is discussed.     

Thermal effects on acid hydrolysis of cellulose

Acid-catalysed hydrolysis of cellulose is a technically feasible process. Cellulosic biomass often requires size reduction which imparts additional cost to the hydrolysis process. A simplified heterogeneous model was developed to study the effect of non-uniform temperature distribution inside wood chips on the hydrolysis process. Increasing particle size was found to result in lower glucose yields and higher reaction times. The effect was more pronounced at higher reaction temperatures. Mathematical correlations were found to quantify this effect.