Citric acid production from partly deproteinized whey under non-sterile culture conditions using immobilized cells of lactose-positive and cold-adapted Yarrowia lipolytica B9.

The present study was performed to produce citric acid (CA) from partly deproteinized cheese whey (DPCW) under non-sterile culture conditions using immobilized cells of the cold-adapted and lactose-positive yeast Yarrowia lipolytica B9. DPCW was prepared using the temperature treatment of 90°C for 15min. Sodium alginate was used as entrapping agent for cell immobilization. Optimum conditions for the maximum CA production (33.3g/L) in non-sterile DPCW medium were the temperature of 20°C, pH 5.5, additional lactose concentration of 20g/L, sodium alginate concentration of 2%, number of 150 beads/100mL and incubation time of 120h. Similarly, maximum citric acid/isocitric acid (CA/ICA) ratio (6.79) could be reached under these optimal conditions. Additional nitrogen and phosphorus sources decreased CA concentration and CA/ICA ratio. Immobilized cells were reused in three continuous reaction cycles without any loss in the maximum CA concentration. The unique combination of low pH and temperature values as well as cell immobilization procedure could prevent undesired microbial contaminants during CA production. This is the first work on CA production by cold-adapted microorganisms under non-sterile culture conditions. Besides, CA production using a lactose-positive strain of the yeast Y. lipolytica was investigated for the first time in the present study.

Tris-sucrose buffer system: a new specially designed medium for extracellular invertase production by immobilized cells of isolated yeast Cryptococcus laurentii MT-61.

The aims of the present study were to isolate new yeasts with high extracellular (exo) invertase activity and to investigate the usability of buffer systems as invertase production media by immobilized yeast cells. Among 70 yeast isolates, Cryptococcus laurentii MT-61 had the highest exo-invertase activity. Immobilization of yeast cells was performed using sodium alginate. Higher exo-invertase activity for immobilized cells was achieved in tris-sucrose buffer system (TSBS) compared to sodium acetate buffer system and potassium phosphate buffer system. TSBS was prepared by dissolving 30 g of sucrose in 1 L of tris buffer solution. The optimum pH, temperature, and incubation time for invertase production with immobilized cells were determined as 8.0, 35 °C and 36 h in TSBS, respectively. Under optimized conditions, maximum exo-invertase activity was found to be 28.4 U/mL in sterile and nonsterile TSBS. Immobilized cells could be reused in 14 and 12 successive cycles in sterile and nonsterile TSBS without any loss in the maximum invertase activity, respectively. This is the first report which showed that immobilized microbial cells could be used as a biocatalyst for exo-invertase production in buffer system. As an additional contribution, a new yeast strain with high invertase activity was isolated.

Utilization of chicken feather hydrolysate as a novel fermentation substrate for production of exopolysaccharide and mycelial biomass from edible mushroom Morchella esculenta.

This study was performed to investigate the usability of chicken feather hydrolysate (Chicken feather peptone (CFP)) as substrate for mycelial biomass and extracellular polysaccharides (EPS) production from edible mushroom Morchella esculenta. The ability of CFP to support biomass and EPS production in edible mushroom M. esculenta was compared to those of two commercial peptones (Tryptone peptone (TP) and Fish peptone (FP)). The maximum biomass (16.3 g/l) and EPS (4.8 g/l) concentrations were achieved with TP. Second, high biomass (15.9 g/l) and EPS (4.6 g/l) concentrations were obtained with CFP. Also, biomass and EPS concentrations in CFP medium were statistically near to those in the TP medium. CFP and TP resulted in not only uniform pellets with smaller size (5 mm) but also faster mycelial growth compared to FP. This study showed for the first time that CFP could be effectively used as a novel EPS production substrate.

Recovering effects of aqueous extracts of some selected medical plants on the teratogenic effects during the development of D. melanogaster.

In this study the effects of some selected medical plants (Pimpinella anisum L., Rosmarinus officinalis L., Achillea millefolium L., Acorus calamus L., Hypericum perforatum L.) on the development of Drosophila melanogaster have been investigated. When the different concentration of plant extracts were applied to the cultures of Drosophila melanogaster, they did not caused an elongation of metamorphosis of F1 progeny. Furthermore, depending on an increase of plant extract on the application groups, the number of offsprings increased. But this increasing (for application groups no. I, II and IV) was not statistically significant (p > 0.05) according to control group. The highest increase in the total number of offspring of F1 progeny obtained from applications of Acorus calamus extracts and the 10 mL/100 mL medium concentration of the extract of Hypericum perforatum.