Annamaria Marzetti

Fractionation and bioconversion of steam-exploded wheat straw

Abstract Wheat straw was pretreated by steam explosion under various conditions. The capability of the process in inducing a high fractionation of the lignocellulosic material in its major components and the influence of the explosion conditions on the substrate susceptibility to the attack of cellulolytic enzymes have been investigated. Bioconversion was studied considering the cellulose-rich fraction obtained from product fractionation as well as the product directly obtained from the explosion treatment. Quantitative data in terms of rate and yield of hydrolysis have been obtained for the different conditions.

Steam exploded biomass for the preparation of conventional and advanced biopolymer-based materials

Abstract Lignocellulosic materials treated by the steam explosion technique alone, or in the presence of chemical reagents, undergo remarkable modifications at the level of both the chemical composition and supramolecular structure, developing features suitable for the production of conventional and advanced materials with improved properties. Experience in the production of high yield pulps, composite materials with microbial (PHB) and synthetic (polypropylene) thermoplastic matrices and high modulus lignocellulosic fibers is reported.

β-d-Galactosidases immobilized on soluble matrices: Kinetics and stability

Abstract Three β- d -galactosidases (β- d -galactoside galactohydrolase, EC 3.2.1.23) from different origins have been immobilized on sucrose-polyacrolein and sucrose sulphate-polyacrolein. This gave enzyme conjugates insoluble in the immobilization medium but which could be made soluble by reduction with sodium borohydride before use. The optimum conditions for both copolymer synthesis and the immobilization reaction were investigated. I.r. and 13 C n.m.r. spectroscopy were used to follow the sulphation and the copolymerization reaction. The characteristics of the enzyme conjugates were compared with those of the free enzymes: the V max values of the enzyme conjugates were lower than those of the corresponding free enzymes, whilst the K m values were similar. The thermal stability of the enzyme conjugates depended on the enzyme origin, while their pH stability was in all cases higher than that of the free enzymes. These data suggest some advantages in using enzyme immobilization supports which can be made soluble after separation of the immobilized enzyme without altering the enzyme characteristics .

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

Abstract The hydrolysis of malto-oligosaccharides G 3 -G 6 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 0.1 m H 2 SO 4 at 70°. Mathematical models for the mechanism of hydrolysis were developed and a good rationalisation of the experimental results was achieved.