Ortansa Csutak

Increase of Saccharomyces cerevisiae plating efficiency after treatment with bipolar electric pulses

Abstract Survival rate of yeast cells after electroporation with a succession of bipolar pulses was investigated. Field strength values from 0 to 1.5 kV/cm with a 8 ms width of pulses succession were used. After the electric treatment, cells were immediately inoculated in YEPG medium and kept 2 h at 30°C. Then cells were plated on standard solid medium and two days later, platting efficiency was recorded. A maximum of UFC appears around the value of 0.85 kV/cm, the number of the obtained colonies being about 100% higher than the lowest value of the field used.

Genetically Modified Microorganisms: Harmful or Helpful?

The history of humanity and economic growth have always been associated with a range of foods, such as bread, beer, wine, meat, and dairy products. Knowledge of the microorganisms involved in food processing and preservation has increased over the last 200 years and the rapid development of molecular biology techniques has allowed a deeper understanding of the genetic backgrounds and specific microbial metabolic pathways. Therefore the genetic improvement of microbial strains involved in food processing may represent a viable solution for globalization of the food and agriculture markets. This chapter deals with some of the most relevant results obtained when using genetically modified lactic acid bacteria and yeast in the food industry. The benefits and hazards are discussed and a glimpse into the current legislation and public concerns is also provided.

Fatty Acids Effect on Lipase and Biosurfactant Induction in Rhodotorula Glutinis CMGB-RG5

Abstract Fatty acids represent important substrates for obtaining microbial lipases and biosurfactants. The yeast strain CMGBRG5 was identified as Rhodotorula glutinis using the BIOLOG MicroLog System. The opacity screening tests showed that R. glutinis CMGB-RG5 was able to produce lipases in presence of 1% Tween 80 after three days of incubation. Lipase induction was estimated as cell growth in presence of Tween 80, Tween 20, olive oil and tributyrin. After 48 hours, best results were obtained in presence of butyric acid, respectively, oleic acid: 2.2 × 107 cells/ml on tributyrin and 1.0 × 107 cells/ml on olive oil. Biosurfactant production was evaluated as emulsification index (E24%). After one week, high E24 values were obtained on fried sunflower oil (53%) and olive oil (35%). Crude and concentrated biosurfactants were tested against nine Candida strains. Best antimicrobial activity was observed for [20X] biosurfactants against C. tropicalis, C. guilliermondii and C. krusei. In conclusion, R. glutinis CGB-RG5 shows high potential for using fatty acids from various sources as unique carbon substrates for synthesis of biocompounds with high economic and biotechnological value.