Sevgi Ertuğrul Karatay

Improving the lipid accumulation properties of the yeast cells for biodiesel production using molasses

In this article the high lipid accumulation potential of Candida lipolytica, Candida tropicalis and Rhodotorula mucilaginosa cells were shown in molasses medium. Four different pH values were examined (4-7) to discover the optimum lipid accumulation medium. Varied concentrations of (NH₄)₂SO₄ (0.5, 1.0, 1.5 g/L) and molasses (6%, 8%, 10%) were tested to find the optimum carbon and nitrogen amounts for the highest cellular lipid production. It is shown that the maximum lipid content could be achieved in the medium containing 8% molasses solution and 1.0 g/L (NH₄)₂SO₄ at pH 5 after four days of incubation time. The maximum lipid contents and methyl ester yields were measured as 59.9% and 84.9% for C. lipolytica, 46.8% and 93.2% for C. tropicalis, 69.5% and 92.3% for R. mucilaginosa. Because of the dominant fatty acids were C16 and C18 in the lipids of yeast cells, these crude lipids could be promising feedstock for biodiesel production.

Bioremoval of textile dyes with different chemical structures by Aspergillus versicolor in molasses medium.

Bioremoval of 17 dyes with different chemical structures by Aspergillus versicolor was detected in this study. Maxilon Red GRL (MR-GRL), Everdirect Fast Black VSF (EFB-VSF) and Brillant Blue R (BB-R) were removed better by fungal mycelia. Optimum pH values were found as 6 for all three dyes. In further experiments in the highest dye concentrations tested in this study, 58.3, 100 and 49% removal yields and 14.8, 12.6, 9.0 q(m) values were found for MR-GRL, EFB-VSF and BB-R, respectively. Chemical oxygen demand (COD) reduction after seven days of incubation period and role of laccase activity of Aspergillus sp. were also investigated. COD reduction and laccase activities were 55.6% and 2.93 U/mL for MR-GRL, 90.7% and 3.0 U/mL for EFB-VSF and 69.0% and 1.79 U/mL for BB-R, respectively. According to these results A. versicolor deserves notable attention for removal of these dyes in wastewater effluents.

EVALUATION OF BIOTECHNOLOGICAL POTENTIALS OF SOME INDUSTRIAL FUNGI IN ECONOMICAL LIPID ACCUMULATION AND BIOFUEL PRODUCTION AS A FIELD OF USE

Considering the vast number of scientific reports on various potential uses of fungi, there was an attempt to select the best lipid producer of some fungi at optimized conditions (Aspergillus versicolor, Rhizopus oryzae, Rhizopus arrhizus, Tramates versicolor). The aim was to offer new fields of use to the industries already culturing and using such materials. Aspergillus versicolor mycelia were found to be accumulating the highest amount of lipids. Experiments to improve lipid accumulation and transesterification properties were performed in molasses medium; the first steps were testing the effects of different pH values and different nitrogen sources on lipid accumulation. Various concentrations of KNO3 (0.5, 1.0, 1.5 gL−1) and molasses (6%, 8%, 10%) were tried in order to find the optimum carbon and nitrogen requirements. Maximum lipid content was 22.8% in the samples containing 6% molasses solution and 1.0 gL−1 KNO3 at pH 4 after 10 days of incubation. The highest fatty acid ethyl ester yield of these samples was 77% (5.0 ethanol:oil, 0.4 sulfuric acid:oil at 30°C for 6 hr). Since the crude lipids were rich in C16 and C18 fatty acids, this was considered as suitable feedstock for biodiesel production.

Effective biosorption of phenol by the thermophilic cyanobacterium Phormidium sp.

The use of microbial biomass as biosorbent for phenol removal has been extensively studied, but its removal by biosorption by thermophilic cyanobacterium Phormidium sp. has not been investigated to the best of our knowledge. In the present study, some important parameters for biosorption process were optimized, starting with testing the effects of different pH values ranging from 1 to 12, and then initial phenol concentrations of 45.1, 115.3, 181.4, 243.3, 339.9 mg/L on phenol uptake. The efficiency of removal from aqueous solution was higher within the pH 6-8 range, with the maximum of 100% at pH 7 after 24 hours of adsorption time. The highest specific rate was observed as 165.1 mg/g in the presence of 339.9 mg/l initial phenol concentration. The Freundlich adsorption models were fitted to the equilibrium data, which indicated that phenol ions were favourably adsorbed by Phormidium sp.

Determination of methylene blue biosorption by Rhizopus arrhizus in the presence of surfactants with different chemical structures.

Methylene blue (MB) biosorption properties of Rhizopus arrhizus were investigated in the presence of surfactants. The effects of cationic and anionic surfactants on MB removal by dead biomass (1 g L−1) were determined. MB removal was tested as a function of initial pH (2–12), contact time (5–1440 min), and dye (37.4–944.7 mg L−1) and surfactant (0–10 mM) concentrations. The opposite charged anionic surfactant dodecylbenzenesulfonic acid sodium salt (DBS) enhanced sorption of cationic MB by biomass dramatically. Maximum biosorption capacity was 471.5 mg g−1 at pH 8 with 0.5 mM DBS at 944.7 mg L−1 MB concentration. The surfactant-stimulated fungal decolorization method may provide a highly efficient, inexpensive, and time-saving procedure in biological wastewater treatment technologies.

Introducing a new salty waste for second-generation bioethanol production

ABSTRACT We have introduced the discards of turnip juice as a raw material for bioethanol production for the first time. Pretreatment methods, initial biomass loading, and fermentation time were investigated. Supplementation of different kinds of nitrogen sources, mineral salts and agricultural waste hydrolysates were added in the growth medium. The highest bioethanol concentrations and Qp values were 7.32, 5.34, 1.55 g/L and 0.61, 0.44, 0.05 g/L.h for S. cerevisiae, K. marxianus and P. stipitis, respectively. Furthermore, Yp/s values were 0.46 g/g, 0.47 g/g, and 0.37 g/g for the three yeasts. Turnip juice discards are promising raw materials for bioethanol production.