A mathematical model applied to the fungal colony growth of Sclerotium rolfsii

Colonies of Sclerotium rolfsii growing on solid medium showed a linear increase in radius simultaneously with exponential changes in colonial weight. The mathematical model developed by Koch (Koch, A.L. 1975. J. Gen. Microbiol. 89, 209216) to describe similar kinetics of mycelial growth was applied. Most of the parameters defined in the mentioned model were directly measured or calculated, except the values of K (maximum mycelium carrying capacity) and S (initial mycelial density) which were fitted to the experimental data of growth at 30°C and 23°C. The ratios K/S at 30°C and at 23°C were 18.8 and 1200 respectively, being consistent with two-dimensional growth. The model was predictive only during the exponential increase of the colony weight.     

Influence of the burning of sugar cane prior to its harvesting upon the production of single-cell protein from bagasse pith

Summary A culture of Cellulomonas sp. and Bacillus subtilis was grown using sugar cane bagasse pith from unburnt sugar cane (UCP) as the source of carbohydrates. The yield and production values were proved to be higher than those obtained with burnt sugar cane (BCP).For UCP the maximum protein production was 7.8 g/l, the cellulolytic activity being 70 %, with a protein/hydrolyzed pith yield of 22 %. For BCP, the maximum protein value was 4.6 g/l, with a cellulolytic activity of 55 % and a protein/hydrolyzed pith of 17 %.The possibility of a chemical inhibitor being present in BCP is discarded because of the alkaline pretreatment and the results obtained on treating the pith from burnt cane with a benzene-ethanol (2:1) mixture. These results were the same as the ones obtained without the benzene-ethyl alcohol mixture extraction.     

Fluidized bed ion exchange for improving purification of lactic acid from fermentation

A strong anionic exchange resin was used to recover lactic acid directly from fermentation in an upflow fluidized bed column, resulting in 0.18 g lactic acid/g resin bound with a subsequent elution of 94%. When the culture broth was heated and adjusted pH to 8.0, 0.4 g lactic acid was bound per g resin, with a subsequent elution of 90%. L(+) and D(–) lactic acid isomers distribution was analyzed in the elution product resulting in an increase of L(+) isomer concentration. The resin did not alter its binding capacity after 23 cycles.     

Quantitative cytochemistry of the diaminobenzidine cytochrome oxidase reaction product in mitochondria of cardiac muscle and pancreas

The rate constant (k) of the cytochrome oxidase reaction under optimal conditions for cytochemical staining (i.e., 15 min fixation, incubation for 180 min for heart, 120 min for pancreas) can be used as a measure of the enzyme concentration within mitochondria. The rate constant derived from microdensitometric measurements of the mass thickness of the 3,3'-diaminobenzidine (DAB) cytochrome oxidase reaction in cristae times correlated data derived from morphometry on the surface density of cristae (SVcristae/Vmit micron-1) and the volume density of mitochondria per cell (Vmit/Vcell) has been used to determine the respiratory index (RI) of these tissues according to the following equation: RI = k(SVcristae/Vcell). Using this formula, the RI of cardiac muscle tissue was computed to be 33 times the RI of pancreas under the conditions of our experiments. The greater cristae surface density and the large mitochondrial volume density in cardiac muscle and high k value accounted for the higher RI of cardiac muscle.     

Single cell protein production from bagasse pith pretreated with sodium hydroxide at room temperature

Summary Previous publications have revealed that a pretreatment of lignocellulosic wastes is necessary if they are to be employed as the hydrocarbon source of single cell protein production. A hot alkaline treatment is the most common.We have treated sugar cane bagasse pith with 1% NaOH solution at room temperature, at a NaOH/pith ratio of 10%. Different contact times were used in the experiments. The shortest contact period required for maximum protein production was 24 h at 25° C. A mixed culture of Cellulomonas sp. and Bacillus subtilis was used in the experiments. The values obtained for hemicellulose and cellulose in the treated pith did not differ greatly from those of untreated pith, in contrast the amount of lignin was 33% lower in the treated pith. The effect of reutilization of the alkaline liquor used for the pretreatment of pith upon protein production was also investigated. With four recyclings, there was a NaOH saving of 34.4 kg per 100 kg produced protein as compared to when the liquor was only used once.The quality of the resulting effluents, as measured by the chemical oxygen demand (COD), proved to be very similar for both types of treatment.     

Determining biomass in viscous culture broths of Sclerotium rolfsii during β-glucan production: hexosamine assay as an indirect alternative technique

Micro-Kjeldahl determination of protein content in the cells was not suitable for the determination of biomass because of the changing composition of the cells. The significant correlation was found during cultivation between the values of the hexosamine assay and those corresponding to the dry weight method (r = 0.98, slope = 1.04) which showed the validity of both hexosamine and dry weight methods, with the former being a simple, reliable and not time consuming alternative for the biomass estimation of Sclerotium rolfsii during scleroglucan production.