Alcoholic fermentation with flocculant Saccharomyces cerevisiae in fed-batch process.

Studies have been conducted on selecting yeast strains for use in fermentation for ethanol production to improve the performance of industrial plants and decrease production costs. In this paper, we study alcoholic fermentation in a fed-batch process using a Saccharomyces cerevisiae yeast strain with flocculant characteristics. Central composite design (CCD) was used to determine the optimal combination of the variables involved, with the sucrose concentration of 170 g/L, a cellular concentration in the inoculum of 40% (v/v), and a filling time of 6 h, which resulted in a 92.20% yield relative to the theoretical maximum yield, a productivity of 6.01 g/L h and a residual sucrose concentration of 44.33 g/L. With some changes in the process such as recirculation of medium during the fermentation process and increase in cellular concentration in the inoculum after use of the CCD was possible to reduce the residual sucrose concentration to 2.8 g/L in 9 h of fermentation and increase yield and productivity for 92.75% and 9.26 g/L h, respectively. A model was developed to describe the inhibition of alcoholic fermentation kinetics by the substrate and the product. The maximum specific growth rate was 0.103 h(-1), with K(I) and K(s) values of 109.86 and 30.24 g/L, respectively. The experimental results from the fed-batch reactor show a good fit with the proposed model, resulting in a maximum growth rate of 0.080 h(-1).

Infection and colonization by Staphylococcus aureus in a high risk nursery of a Brazilian teaching hospital.

Neonates are susceptible to nosocomial infections due to immunological immaturity, prolonged hospital stay and the use of invasive procedures. We evaluated the incidence of infections and the prevalence of colonization by MRSA (Methicillin-resistant Staphylococcus aureus) and MSSA (Methilin-susceptible Staphylococcus aureus), as well as colonization risk factors. Staphylococcal infections were observed by analyzing medical records in the HICS (Hospital Infection Control Service) and the HRN (High Risk Nursery). Additionally, four inquiries concerning colonization prevalence were made for S. aureus, from January/2000 to December/2002. Clinical specimens from the nostrils, mouth and anus were cultivated in mannitol-salt agar plates and identification was made through standard methods. The frequency of neonates colonized by S. aureus was 49%. MSSA was more prevalent (57%) than MRSA (43%). Risk factors related to the acquisition of MRSA were: low weight and antibiotic use., Hospital stay was the only variable significantly associated with colonization by S. aureus. The incidence of infections by S. aureus during the last three years was 2.18% (159 cases). Nine of them (5.5%) were associated with MRSA and 150 (94.5%) with MSSA. Staphylococcal infections were considered as invasive (sepsis) and non-invasive (conjunctivitis, cutaneous), corresponding to 31% and 69%, respectively. The MRSA phenotype in infection was rare compared with methicillin-susceptible samples, although S. aureus, MRSA and MSSA colonization rates were high.