Process optimization of batch biosorption of lead using Lactobacillius bulgaricus in an aqueous phase system using response surface methodology.

Response surface methodology (RSM) based on central composite rotatable design was used to investigate the effects of operating variable, mainly, pH, weight of biomass, and initial lead ion concentration on the lead adsorption capacity at ambient temperature using dried cells of Lactobacillius bulgaricus. Using RSM, quadratic polynomial equation was obtained for predicting the percent of lead ion removal. Analysis of variance showed that the effects of pH and weight of dried biomass were concluded to be the key factors influencing the capacity of lead ion removal. At pH lower than 2 (high acidic condition) and in alkaline condition, there is no significant biosorption. The optimum percent of lead ion removal was found at pH of 6.78, biomass concentration of 6.58 g/l and initial lead concentration 36.22 ppm. In this condition, percent of lead ion removal was 86.21%. This study showed RSM effectiveness for modeling of biosorption process.

Antagonistic potentiality of Trichoderma harzianum towards seed-borne fungal pathogens of winter wheat cv. Protiva in vitro and in vivo.

The antagonistic effect of Trichoderma harzianum on a range of seed-borne fungal pathogens of wheat (viz. Fusarium graminearum, Bipolaris sorokiniana, Aspergillus spp., and Penicillium spp.) was assessed. The potential of T. harzianum as a biocontrol agent was tested in vitro and under field conditions. Coculture of the pathogens and Trichoderma under laboratory conditions clearly showed dominance of T. harzianum. Under natural conditions, biocontrol effects were also obtained against the test fungi. One month after sowing, field emergence (plant stand) was increased by 15.93% over that obtained with the control treatment, and seedling infection was reduced significantly. Leaf blight severity was decreased from 22 to 11 at the heading stage, 35 to 31 at the flowering stage, and 86 to 74 at the grain filling stage. At harvest, the number of tillers per plant was increased by 50%, the yield was increased by 31.58%, and the 1,000-seed weight was increased by 21%.

Development of predictive models for the growth of Escherichia coli O157:H7 on cabbage in Korea.

Cabbage is the main material of coleslaw, a popular side dish in Korea as well as many other countries. In the present study, the combined effect of temperature (15, 25, and 35 °C) and relative humidity (60%, 70%, and 80%) on the growth of Escherichia coli O157:H7 on cabbage was investigated. The polynomial models for growth rate (GR), lag time (LT), and maximum population density (MPD) estimated from the Baranyi model were conducted with high coefficients of determination (R(2)> 0.98). Subsequently, performance and reliability of the models were assessed through external validation, employing three indices as bias factor (B(f)), accuracy factor (A(f)), and the standard error of prediction expressed in percentage (%SEP). The B(f), A(f), and %SEP values of the predictive models for GR were 1.008, 1.127 and 18.70%, while 1.033, 1.187 and 20.79% for LT and 0.960, 1.044 and 5.22% for MPD, respectively. The results demonstrated that the developed secondary models showed a good agreement between the observed and predicted values. Therefore, the established models can be suitable to estimate and control E. coli O157:H7 growth risk on cabbage at some steps from farm to table in Korea as a valuable tool.