Comparison of urinary sphingolipids in human populations with high and low maize consumption as a possible biomarker of fumonisin dietary exposure.

The increased sphinganine/sphingosine (SA/SO) ratio has previously been shown as a biomarker of fumonisin exposure in experimental animals and has been proposed as a tool to assess human exposure to fumonisin mainly occurring through the dietary consumption of fumonisin contaminated maize-based foods. Sphinganine and sphingosine were measured in urines of humans resident in two areas of North Argentina and South Brazil with high maize consumption and compared with urine samples collected in areas with very low or no maize consumption, such as Central Argentina and Southern Italy. The pattern of SA/SO values in the two groups with no maize consumption (assumed as controls) was similar, with all SA/SO values lower than one. Mean SA/SO ratio was 1.27 in urine of subjects with high maize consumption (n = 123) and 0.36 in controls (n = 66) and the difference was statistically significant (p<0.001). The mean fumonisin level in maize samples collected in North Argentina and South Brazil was 0.35 mg kg(-1) (n = 40). Although a similar maize and fumonisin intake was recorded for the two groups of populations, the mean SA/SO ratio in South Brazil (1.57) was significantly higher (p<0.05) than that of North Argentina (0.69). These data suggest that the higher SA/SO values observed in South Brazil cannot be associated with high fumonisin exposure and further studies are necessary to provide convincing evidence for using the SA/SO ratio as a biomarker of human fumonisin exposure.

Discrimination between ethanol inhibition models in a continuous alcoholic fermentation process using flocculating yeast.

Discrimination between different rival models for describing the inhibitory effect of ethanol both on yeast growth and on fermentation was studied for a continuous process of alcoholic fermentation in a tower reactor with recycling of flocculating cells. Models tested include linear, parabolic, hyperbolic, exponential, and generalized nonlinear power-law types. The best expressions were identified under the criteria that all the kinetic parameters should assume acceptable values in a feasible range and should result in the best fit of the experimental data. The kinetic parameters were estimated from steady-state data of several sugar concentrations in feeding stream (S0 = 160, 170, 180, 190, 200 g/L), constant dilution rate (D = 0.2 h-1), recycle ratio (alpha = 13.6), and temperature (T = 30 degrees C). The best model for the yeast growth was of power-law type, whereas for the product formation the best model was of linear type. These models were able to reproduce the trends of the process variables satisfactorily.

Continuous alcoholic fermentation process in a tower reactor with recycling of flocculating yeast.

The influence of different substrate concentrations on the performance of a continuous system of alcohol production by fermentation using a tower reactor with recycling of flocculating yeasts was investigated. All experiments were carried out using a flocculating yeast strain IR-2, isolated from fermented food, and identified as Saccharomyces cerevisiae. Cane sugar juice was used as a substrate with sugar concentrations of 160, 170, 180, 190, and 200 g/L. Constant values of dilution rate, 0.20 h-1, temperature, 30 degrees C, and pH 3.3, were used. The performance of the reactor was observed to be efficient with high substrate concentrations. Maximum productivities of 18 g/L/h 99% substrate conversion and ethanol concentrations of 90 g/L were obtained using 200 g/L of sugar in the feedstock. For substrate concentrations of 160 g/L, a maximum yield of 0.45 g of ethanol/g of sugar was observed or 90% of the theoretical value.

Fumonisins in maize genotypes grown in various geographic areas.

Data on the occurrence of fumonisins B1 and B2 in maize genotypes (inbred lines and hybrids) cultivated in several countries from three continents will be presented. Samples originated at different times (from 1990 to 1994) from experimental stations in Argentina, Benin, Croatia, Poland, Portugal, Italy, Romania and Zambia. Fumonisin contamination was negligible in samples from eastern Europe (Croatia, Romania and Poland), whereas it was quite relevant and widespread in samples from Argentina, western Europe and Africa. A general trend of higher fumonisin levels was observed in Argentina, Zambia (limited to 1993 crop), Portugal, and Italy (mainly 1990 and 1991 crop years), with a significant percentage of samples showing more than 1000 ng/g, a level of concern. The data from the present study suggest that the environmental conditions in the specific area of cultivation play an important role in the accumulation of fumonisins in maize.

Natural occurrence of fumonisins and their correlation to Fusarium contamination in commercial corn hybrids growth in Argentina.

Fifty commercial corn hybrids with different endosperm characteristics, vegetative cycle length and cross class grown in the same geographical area (Cordoba Province, Argentina) were analysed for fumonisin accumulation. All hybrids analysed showed fumonisin B(1) and B(2) contamination ranging from 185 to 27,050 ng/g for FB(1) and from 40 to 9950 ng/g for FB(2). Although most of the hybrids analysed had flint-type endosperm, two hybrids with dent-type endosperm (e.g. Prozea 10 and AX 746) showed the highest level of fumonisin (37,000 ng/g) and more FB(2) than FB(1) (FB(2)/FB(1) ratio 2.42), respectively. There was no correlation between fumonisin concentration and length of the vegetative cycle. Among 18 hybrids examined for Fusarium species contamination there was also no correlation between fumonisin contamination and the level of infection with Fusarium species (Section Liseola). Eighteen hybrids showed fumonisin levels lower than 1000 ng/g. This result suggests that there is some possibility of selecting hybrids resistant or less susceptible to fumonisin and Fusarium contamination.