Danley A. S. Callieri

High yield conversion of sucrose into ethanol by a flocculentZymomonas sp isolated from sugarcane juice

SummaryA flocculentZymomonas sp strain was isolated from fermenting sugarcane juice taking advantage of the motility and ethanol tolerance. The capacity of the new isolate to convert glucose and sucrose into EtOH was investigated. using 200 g/l sucrose feed the isolate showed a sucrose uptake and EtOH yield over 3 times higher than those of the test organismZ. mobilis ATCC 10988.

Production of pectinases byAspergillus sp using differently pretreated lemon peel as the carbon source

SummaryAspergillus sp strains from decaying lemons were tested for extracellular pectinase production, testing differently pretreated lemon peel as the carbon source instead of pectin. It was found that the production of extracellular polygalacturonase was about the same and that of pectinesterase substantially higher when unwashed fresh lemon peel was used instead of pectin. The culture filtrate obtained showed a clarifying capacity similar to that of a commercial pectinase preparation, but the vitamin C of the juice was less affected by the treatment.

Ethanol production by a mixed culture of flocculent strains of Zymomonas mobilis and Saccharomyces sp.

Abstract Pure and mixed cultures of Zymomonas mobilis and Saccharomyces sp. were tested for the production of ethanol using sucrose as the carbon source. Both strains, isolated from spontaneously fermenting sugar-cane juice, are flocculent and alcohol-tolerant. The best results were obtained using a mixed culture, with a yield of 0.5 g ethanol/g sugar consumed and a volumetric productivity of 1.5 g ethanol l-1 h-1. No levan was produced even if a sucrose-based medium was used.

Production of ethanol by yeasts immobilized in pectin

SummaryYeasts cells (Saccharomyces cerevisiae) were immobilized by occlusion in pectin gel, no significant changes in their biological activity being observed. The ethanol production rate was found to be negatively affected by the diameter of the beads when the cell concentration in them was high. The fermentative activity was only slightly modified by pectin concentration. Cells maintained their growth capacity and the beads could be reutilized several times in succesive batch fermentations. After freeze-drying and storage at room temperature the beads retained both their morphological and mechanical characteristics as well as 93% of their initial fermentative activity.

Batch culture of Candida utilis in a medium deprived of a phosphorous source

SummaryCandida utilis var. major NRRL-Y-1084 was grown in a defined medium without a phosphorous (P) source. During the exponential phase, cells divided according to a specific growth rate of 0.32 h-1, which is lower than the usual rate for a balanced medium (0.4–0.6 h-1). The relative P content of the biomass decreased from 2.70% to 0.75% over a period of 6 h, including 2 h of cell division arrest. At the end of this period there was another interruption of cell division. After that, multiplication restarted at a considerably lower rate and it deviated slightly from the exponential pattern. The stationary phase began when biomass P content reached 0.4%–0.5%, slowly decreasing afterwards to 0.25–0.20%. Biomass synthesis was less affected than cell division by the relative decrease of endogenous P, the two processes differing partially in their kinetics. Cell lysis started shortly before the stationary phase and affected about 20% of the population by the end of the assay. RNA and P content of the resulting biomass were 2.4% and 0.25% respecitvely, P being mainly incorporated to RNA.The relationship of biomass production to glucose uptake was very low, probably because the marked P deficiency called for an increase in energy consumption for growth and specially for maintenance. Compared with yeasts grown in a balanced medium, 40% increase in glycogen was observed, whereas no mean changes in the content of cell wall carbohydrates (glucan and mannan) and that of “true protein” were found.

Composition and morphology of Candida utilis grown in continuous culture with decreasing concentrations of phosphate

Candida utilis was grown in continuous culture with decreasing concentrations of phosphate. At a constant dllution rate three successlve growth patterns were observed: carbon-limited growth, carbon and phosphate dual-limited growth, and phosphatelimited growth. Phosphate deficlency as well as phosphate limitation produced significant modifications in cell composition and morphology, including cell size. At the lowest phosphate concentration (6 mg/P/I), the cell size was the largest and the relative contents of phosphorus and RNA in the cells was very low, with 96% of the total phosphorus being located in the RNA fraction.

Studies on the polyphosphate cycle in Candida utilis: effect of dilution rate and nitrogen source in continuous culture

Candida utilis cells were grown in continuous culture in a medium with ammonium or arginine as the nitrogen source. The present paper describes the influence of changes in specific growth rate on the storage of arginine and polyphosphates, as well as on the length of the polyphosphate chain in continuous culture

Conversion of sucrose to ethanol by a flocculent Zymomonas sp. strain in a continuous upflow floc reactor

SummaryA flocculent strain of Zymomonas sp. isolated from sugar cane juice was used to produce ethanol (EtOH) from sucrose in a 50 ml upflow floc continuous reactor. A maximun productivity of 92 g EtOH/l per hour (estimated on a total volume basis) with 10% sucrose feed and 60% conversion to ethanol was achieved at a dilution rate (D) of 3 h−1. At D=2 h−1 the productivity was 80 g EtOH/l per hour and the yield 0.4 g EtOH/g sucrose supplied. Dilution rates up to 7 h−1 were assayed and even when no wash out occurred, productivity dropped to 63 g EtOH/l per hour and conversion was very low (16%). These results are compared with those obtained using Zymomonas mobilis ATCC 10988 under the same conditions.

Studies on the polyphosphate cycle in Candida utilis

SummaryCandida utilis cells were grown in continuous culture in a medium with ammonium or arginine as the nitrogen source. Arginine produced a marked change in the amount of polyphosphates and arginine in whole cells and vacuoles, as well as in the ratio of the concentrations of these substances. The specific growth rate (μ) which in continuous culture is equivalent to the dilution rate (D), affects the amount and chain length of the polyphosphates and also the arginine content of the vacuoles and whole cells. Thus, if D is increased the amount of polyphosphates per milligram protein is increased. There is apparently a direct and linear relationship between D, the specific growth rate (μ) and the polyphosphate content. Changes in D also affect the length of the polyphosphate chain, and the relationship is inverse. At low growth rates, two types of chain were observed, one of approximately 35 phosphate units and the other of 5 units. At high growth rates phosphorus was not stored as longchain polyphosphates.

Determination of the optimal conditions for the continuous culture of Candida utilis in sugarcane stillage

SummaryCandida utilis was continuously cultured in sugarcane stillage without any supplementation, but the yeast utilized the stillage nitrogen only partially. As a result, the cell biomass production was low and the residual chemical oxygen demand (COD), as well as the total nitrogen content of the effluent were high. The addition of 2–4 g/l ammonium phosphate and small amounts of Fe2+, Cu2+, and Zn2+, markedly enhanced both the everall nitrogen uptake and cell biomass production, decreased COD, and a higher critical dilution rate was attained. No substantial differences were found when pH was kept at 5.0 or allowed to evolve freely. The optimal temperature range was between 30 and 35°C.