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Ammonium fumarate production from glucose-based media by Rhizopus arrhizus NRRL 1526 with mycelial growth controlled by phosphorus limitation exhibited mixed-growth-associated product formation kinetics, with growth-associated production related to secondary mycelial growth only. The contribution of the primary mycelial growth phase was minimised by resorting to prolonged batch production using free mycelia under intermittent glucose feeding or repeated batch production using immobilised mycelia. The metabolic activity of free or immobilised mycelia was limited by fumarate accumulation or by oxygen diffusion phenomena, respectively. For batch cultures in a 15 dm³ stirred bioreactor the peripheral impeller speed (v_I) was increased from 1.88 to 3.3 m s^-1, and the fumarate yield coefficient on glucose increased from 0.25 ± 0.01 to 0.42 ± 0.02 g g^-1, while the malate yield coefficient on fumarate (Y_M/F) reduced from 0.46 ± 0.01 to 0.14 ± 0.01 g g^-1. With a net increase in the fumarate-to-malate ratio from 2 to 6.5, a v_I value of 3.3 m s^-1 gave the best fermentation performance and provided a basis for further scale-up studies.© 2002 Society of Chemical Industry

The antibacterial effect of different glucose oxidase (GOX)/glucose combinations was studied on two food-poisoning organisms, enterotoxic Escherichia coliPM 015 and Salmonella derbyBP 177. Growth of E. coliin nutrient broth (NB) was clearly inhibited by 4.0 mg/ml glucose after 24 h when combined with 2.0 U/ml GOX and after 48 h when combined with 0.5 or 1.0 U/ml GOX. Salmonella derbywas more resistant than E. coli, but showed clear growth inhibition only after 48 h when inoculated in tubes where 2 mg glucose/ml and 2 U GOX/ml (or 4 mg glucose/ml and 1 U GOX/ml) were combined. In order to understand if the enzyme effect on microbial growth can be attributed to hydrogen peroxide or to pH decrease as a result of the production of gluconic acid, catalase (CAT) was added to GOX/glucose system. Since CAT decomposes H2O2to H2O and O2, the antibacterial effect was ascribed to a pH decrease as a result of gluconic acid in the system.

Starchy materials such as corn starch, soft wheat flour, potato flour, cassava flour, sorghum starch, sweet potato and industrial potato flours, either acid or enzymatically hydrolysed, were used as substrates for itaconic acid production by Aspergillus terreusNRRL 1960. Both production and yield were highest on corn starch (18·4 g l−1and 34·0%, respectively). The degree of hydrolysis had a great influence on acid production which was highest when corn starch was saccharified at 85 DE (dextrose equivalent). In a 3 litre benchtop fermenter, itaconic acid production and productivity were 19·8 g l−1and 0·13 g l−1h−1, respectively.

Fumaric acid production by Rhizopus arrhizus from potato flour was studied at different initial substrate concentrations (S), C/N ratios and fermentation times (tf) in a composite design experiment. By using response surface methodology and canonical analysis, the experimental values of fumaric acid and mycelial biomass yields and productivity were fitted to the only statistically significant factors with mean percentage errors of 11, 26 and 13%, respectively. Owing to the limited statistical significance of the C/N ratio, it was possible to determine the values of S (25–50 g/l of glucose equivalent) and tf(44–100 h) associated with fumaric acid yields ranging from 60 to 75% and productivities varying from 6 to 8.4 g/l per day. Since such results were in quite good agreement with previous experiments carried out on other starchy materials, the above operating conditions might be used to minimize fumaric acid production costs as a function of the feed-stock used.

Light-microscope findings and pathological ultrastructural changes in sural nerve biopsies from two patients affected by hypothyroidism, one with overt signs of peripheral neuropathy, the other asymptomatic, were studied. In both patients the endoneural vessels showed clear pathological changes similar to those of other metabolic neuropathies, but more marked in the symptomatic patient. It is proposed that the changes observed in the nerve fibers in hypothyroid neuropathy are secondary to changes in the endothelial cells and in the vessel wall.

Fifty-eight strains, representing 31 species of Penicillium, were screened for extracellular ß-glycosidase (amygdalase/linamarase) and pectolytic (polygalacturonase, pectin lyase) enzymes. One strain each of P. turbatum, P. piceum and P. paxilli showed very high ß-glycosidase activity and slightly lower activities were found in P. crustosum, P. expansum, P. oxalicum and P. aurantiogriseum. Generally, maximum ß-glycosidase activity showed reached during the stationary phase of growth. The seven species with highest ß-glycosidase activity showed different patterns of pectolytic activities, indicating that different species or combinations of species could be selected for different potential applications.

We performed a morphological, morphometric and toxicological study on the spinal ganglia and peripheral nerves of the rat after chronic administration of cisplatin (cis-dichlorodiammineplatinum II; DDP) with two different schedules. Severe damage of the spinal ganglia neurons was demonstrated with predominant involvement of the nucleus and nucleolus associated with a decrease in the cell size. Morphological and morphometric changes also occurred in the sciatic and peroneal nerves with the features of axonopathy. All these changes were more marked in the group of rats which underwent the most intense DDP treatment and the tissue platinum concentrations were also higher in this group. This experimental model is the first available for chronic DDP administration in which concomitant spinal ganglia and peripheral nerve damage has been confirmed pathologically. Our study supports the hypothesis that DDP-induced peripheral nerve fiber degeneration may result from nuclear and nucleolar changes in the sensory ganglion cell perikaryon.

Cryptococcus albidus var. albidus, strain IMAT-4735, grown on suitably treated oil-mill vegetation waters produced pectic enzyme. Growth and enzyme production were favoured by addition of calathide residues from sunflower cultivation, a low-cost pectic material, to the vegetation waters. Ultrafiltration of the centrifuged fermentation broth made it possible to almost completely recover the enzyme activity produced. The enzyme concentrate from ultrafiltration was directly reused in the mechanical extraction of olive oil.

Conidia ofPenicillium variabile P16 were immobilized in polyurethane sponge and used in repeated-batch processes in a fluidized-bed reactor. Optimal conditions for production of glucose oxidase and catalase were: inoculum size, 10%; glucose concentration, 80 g L-1; Ca-carbonate concentration, 15 g L-1; temperature, 28°C and aeration rate, 4 VV-1 min-1. In an extended repeated-batch process, glucose oxidase activity was highest after the fourth batch and catalase activity was highest after the fifth batch. Scanning electron microscopy showed that the fungus grew only in the interior of carrier particles.

Conidia of Penicillium variabileP16 producing glucose oxidase were immobilized in different carriers and used in repeated-batch processes. Limited free-cell growth and good mechanical stability of the carriers were obtained with Ca-alginale, agar and polyurethane sponge. During prolonged experiments, the polyurethane sponge appeared to be the best carrier in relation to glucose oxidase and catalase activities. The maximum mean volumetric productivity of gluconate was obtained using agar as immobilizing agent.

Yeast-like cells ofAureobasidium pullulanswere immobilized in Ca-alginate gel beads and employed for continuous production of glucoamylase in a fluidized-bed reactor (250 ml working volume). After an activation time of 48 h, to allow the “in situ” germination of the fungal blastospores, the reactor was operated continuously for over 150 h. A steady state enzyme concentration of 1.2–1.3 U ml−1of glucoamylase activity and an enzyme volumetric productivity of ca. 130 U ml−1h−1were obtained at a medium flow rate of 26 ml h−1. Enzyme activity and volumetric productivity were influenced by fermentation conditions such as inoculum size and airflow rate.

During screening ofPenicillium species for extracellular glucose oxidase production, a strain ofPenicillium variabile (P16) was selected which released high activities of enzyme into the culture medium. Maximum activity (5.49 U/ml) was after 96 h cultivation in shake-flask culture.