D-amino acid oxidase from Trigonopsis variabilis: immobilisation of whole cells in natural polymeric gels for glutaryl-7-aminocephalosporanic acid production

The enzymatic oxidation of cephalosporin C to glutaryl-7-amminocephalosporanic acid (glutaryl-7-ACA) was carried out utilizing permeabilized whole cells of the yeast Trigonopsis variabilis entrapped in Ca-alginate beads. The biomass, cultured in a rich medium containing D,L methionine and harvested after 72 h of growth, exhibited high levels of D-aminoacid oxidase activity. Prior to use, thewho,lke cells were permeabilized with four freeze-thawing cycles and immobilized in polysaccharide matrices, such as Ca-alginate and K- carrageenan, and in an insolubilised gelatin gel. The best results in terms of activity yield and storage stability were obtained with cells entrapped in Ca-alginate beads. These cells were utilized for glutaryl-7-ACA production in a continuous stirred batch reactor (CSTR) and in a packed bed reactor working in a plug flow reactor (PFR), using 50 mm Cephalosporin C as substrate. The performances of the two systems were compared. The overall on a void volume basis) were 1.63 g and 255 mg of glutaryl-7-ACA h-1 in the PFR and in CSTR, respectively

Effect of polyvinylalcohols on the thermostability of lipase from Candida rugosa

Lipase from Candida rugosa was stabilized against thermal inactivation in the presence of polyvinylalcohols (PVA) of different molecular weights. The apparent rate constant of the lipase inactivation, kd, at 49 °C is 0.049/min and 0.022/min in the absence and in the presence of PVA (mol wt 22,000), respectively. The improvement of the lipase thermostability by adding PVA was confirmed by differential scanning calorimetry. The presence of PVA had also an effect on the hydrolytic activity of the enzyme. Furthermore, lipase was modified by covalent linkage to PVA by means of an original procedure. With respect to the native enzyme, the modified lipase has a slightly lower specific activity, but it is more stable against heat denaturation (kd 0.032/min at 49 °C)

Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy Study of Carbohydrate Decomposition by Hydrothermal Liquefaction Treatment: A Modeling Approach on Bio-oil Production from Organic Wastes

Glucose and cellulose as model compounds were treated under hydrothermal liquefaction (HTL) conditions to describe the main reaction pathways that are involved in the process. The HTL-derived phases (gas phase, bio-oil, aqueous phase, and solid residue) were fully characterized by a combination of analytical techniques [i.e., elemental analysis (EA), gas chromatography–mass spectrometry (GC–MS), electrospray ionization/atmospheric pressure photoionization Fourier transform ion cyclotron resonance–mass spectrometry (ESI/APPI FTICR–MS), and ¹³C cross-polarization–magic angle spinning nuclear magnetic resonance (CP–MAS NMR)], and a comprehensive HTL degradation mechanism was proposed. A wide range of different reactions (dehydration, decarboxylation, retro-aldol, aromatization, condensation, oxidation, and reduction) were found to be involved in the formation of the different compounds detected in the four phases. The main identified products in both glucose and cellulose HTL bio-oils were furfural derivatives, which further react leading to several phenolic and aliphatic compounds. Oligomers arising from the condensation of furfural derivatives were also found, and their polymerization finally results in a solid residue whose characterization confirmed the presence of polyfuranic networks together with graphite-like domains. Finally, glucose and cellulose showed a similar behavior considering the product yields and phase composition, suggesting that the polymerization degree does not significantly affect the HTL process