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Lipases were noncovalently immobilized in Chitoxan, a polyionic hydrogel obtained by complexation between chitosan and xanthan. The properties of free and immobilized lipases have been compared. In the aqueous medium, the activity was twice as high for immobilized lipases as for free lipases. Immobilized lipases in chitoxan were able to hydrolyze triacylglycerols in three distinct organic solvent media. At the microstructural level, lipases were not distributed uniformly in the chitoxan beads. Higher concentrations of lipase were found in the outer membrane-like layer of the beads, as compared with lower concentrations in the inner part of the beads.

Lipases were noncovalently immobilized in Chitoxan, a polyionic hydrogel obtained by complexation between chitosan and xanthan. The properties of free and immobilized lipases have been compared. In the aqueous medium, the activity was twice as high for immobilized lipases as for free lipases. Immobilized lipases in chitoxan were able to hydrolyze triacylglycerols in three distinct organic solvent media. At the microstructural level, lipases were not distributed uniformly in the chitoxan beads. Higher concentrations of lipase were found in the outer membrane‐like layer of the beads, as compared with lower concentrations in the inner part of the beads.

We have investigated the kinetics of methane-ammonia mixture decomposition in a cold plasma. Among the products of methane decomposition H2, C2H6, C2H4and C2H2were identified. Their ratio was dependent on time and discharge of the used power in the experiments. When the ammonia was used as medium, there were identified only H2and hydrazine as reaction products. For the CH4-NH3mixture among the decomposition gases we could find hydrogen cyanide, ethylamine, methylamine and other aliphatic amines.

Ampicillin and chloramphenicol were coupled on xanthan by activation by dicyclohexyl-carbodiimide. Drug release from the support was studied in vitro for ampicillin, and in vitro and in vivo conditions for chloramphenicol.

The coupling of chloramphenicol on Biozan R (Hercules) by activation with dicyclohexylcarbodiimide was studied. The esterification is influenced by the chloramphenicol/dicyclohexylcarbodiimide ratio, concentration of the reactants and reaction time.

New polyimidazolyl and polypyrazolyl esters were synthesized by polycondensation of the chlorides of the pyrazolyl and imidazolyl dicarboxylic acids with ethylene glycol,pentamethylene glycol and glycerol.

Xanthan and its crosslinked beads have many biomedical applications. Xanthan has been reticulated with epichlorohydrin, thus becoming a hydrogel with a swelling ratio in the range 1–10 and having a solvent content of 80–90%. Through its diffusion from alcohol/water mixture (5/1–5/4,v/v) of various concentrations, isosorbide dinitrate has been inserted into the hydrogel. The content of isosorbide dinitrate in the hydrogel varies in the range 40–150 mg/g. The drug is released according to “zero-order” kinetics at a constant rate of 1.5 µg/h, for a duration of 9 h.

In the present paper the immobilization of invertase and amyloglucosidase on Biozan R with dicyclohexylcarbodiimide as a catalyst is studied. The influence of some factors on the coupling reaction (duration, enzyme/support and catalyst/support ratios) as well on the acitvity of the coupled enzyme in followed. For both systems under study the value of the Michaelis-Menten constant is higher for the coupled enzyme than for the free one.

In the present paper the mechanism and kinetics of methane-water mixtures decomposition in cold plasma are discussed. It was found that nature and composition of the products depend on reaction time, ratio of the two components, and how long the products are in contact after the decomposition was performed.

After passage of methane-water mixtures through the state of a cold plasma, numerous products were identified, especially aldehydes, ketones, alcohols and acids. Their concentration was dependent on the methane/water ratio. Irradiation with UV light during or after the process gave transformations of the above compounds to more complex combinations. For the formation of ketones, aldehydes, alcohols and acids a detailed mechanism is proposed.

Polyionic hydrogels have been prepared by complexation of chitosan and xanthan. These hydrogels have been used to immobilize lipase from porcine pancreas (E.C. 3.1.1.3). Immobilization efficiency varied between 90 and 99% of initial activity. Immobilized lipase retained its activity towards hydrolysis of olive oil in water as an emulsion and of olive oil in isooctane.

The ampicillin coupling on BIOZAN R (a polysaccharide of microbial synthesis Xanthomonas campestris) is studied by the activation of carboxylic groups by dicyclohexylcarbodiimide. The following optimum reaction parameters are settled on the basis of an experimental program: time = 7.5 h, temperature = 10 °C, dicyclohexylcarbodiimide concentration = 1.10-3mole, ampicilline concentration = 2.4·10-3mol. Under these conditions up to 37% of ampicillin with respect to the polymer is coupled.

The present paper studies the process of esterification of nalidixic acid on poly(vinyl alcohol). The influence of time, dilution and concentration of the reactants on the efficiency of esterification with dicyclohexylcarbodiimide has been followed. By experiment scheduling according to a centered, rotatory, compound, second order program, optimum conditions for the system under study have been found. On the other hand, the evolution of reaction of esterification of the nalidixic acid on poly(vinyl alcohol) was followed by using the activator-catalyst (4-pirolidinopyridine) system. An increase of the esterification yield up to 37% has been observed.

A method for the preparation of hydrogels from the complexation of chitosan and xanthan is reported. Stable hydrogels capable of retaining be tween 65 and 95% weight water were prepared. The water retention and prop erties of the hydrogels were studied as a function of the degree of acetylation of chitosan and the ratio chitosan/xanthan used in the preparation of the gel. Spectroscopic FTIR was used to confirm complexation between the amine (chi tosan) and carboxylic (xanthan) groups. Electron micrographs (SEM and TEM) show the formation of a fibrillar structure with characteristic pore sizes be tween 100 and 1000 nm and fibril diameters between 50 and 100 nm. The diffu sion coefficient of 4-O-methyl-d-glucurono-D-xylan Remazol Brilliant Blue R (RBB-xylan) in the complex chitosan-xanthan was 2.02 × 10-12m2s-1at 30°C. The chitosan-xanthan complex was used to immobilize two enzymes (endo-1,4- β-xylanase and protease) either as single enzymes or as a binary system. Immo bilization varied between 85 and 98%. The immobilized xylanase activity was significantly greater with respect to the free enzyme while the binary enzyme system promoted protease activity.

Poly(methylmethacrylate-b-styrene) and poly(methylmetha-crylate-b-acrylonitrile) block copolymers are synthesized by means of the 4,4'-azo-bis-(4-cynovaleryl)-benzoyldiperoxide. In the first stage a polymethylme-thacrylate prepolymer is synthesized using the above mentioned initiator.The prepolymer containing peroxide end groups is employed in the second stage for the block copolymerization of styrene or acrylonitrile.The block copolymer structure was elucidated by means of IR and NMR spectral measurements.

A rule based fuzzy logic control is developed for control of lignocellulosic residues saccharification with Aspergillus nigerin a fed-batch bioreactor. The membership functions, fuzzy ranges for the controller input/output are defined. A fuzzy rule base is constructed based on human experts’ knowledge. The performance of the fuzzy-logic controller is evaluated by simulation.

endo-1,4-β-Xylanase (E.C. 3.2.1.8) has been immobilized in hydrogel beads prepared by complexation between chitosan and xanthan. The enzyme immobilization efficiency is between 88 and 98% within a wide range of concentrations of xylanase. The optimum xylanase activity requires a pH between 5.0 and 5.5. The immobilized enzymes show 60−70% higher activity than free enzymes. The Km of the immobilized xylanase increases with the concentration of the enzyme in the beads. The latter show, by electron microscopy, a predominantly fibrilar microstructure within which there are regions having globular shapes where the enzymes are lodged.

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