Sedat Dönmez

Application of microbial enhanced oil recovery technique to a Turkish heavy oil

SummaryMicrobial enhance oil recovery utilizes microorganisms and their metabolic products to improve the recovery of crude oil from reservoir rocks. In this study an anaerobic bacterium, Clostridium acetobutylicum was injected into a one-dimensional model reservoir containing a Turkish heavy oil (Raman oil) at 38° C. This injection was followed by water flooding after a suitable shut-in period. Comparison of oil recovery results of pure water flooding runs with experiments in which bacterial concentration and shut-in periods were varied indicated increases in oil recovery of about 12% of the original oil in place. This increase was attributed to changes in the viscosity and pH of the crude oil.

Optimization of Ethanol Production From Microfluidized Wheat Straw by Response Surface Methodology

In this study, wheat straw was pretreated with a microfluidizer to improve its enzymatic hydrolysis and ethanol yields. The pretreatment was performed at various pressures (500, 1000, and 1500 bar) and solid loadings (1, 2, and 3%). The microfluidized biomass was then subjected to hydrolysis and simultaneous saccharification and co-fermentation (SSCF) experiments at different enzyme loadings (5, 10, and 15 FPU/g dry wheat straw) using a mutant yeast. The results indicated that the microfluidization method alters the structure of biomass and leads to a reduction in lignin content. The samples pretreated at 1% solid loading contained the minimum lignin concentration and provided the maximum sugar and ethanol yields. These results signified that the microfluidization method is more effective on biomass at low solid loadings. The process conditions were optimized for higher ethanol and sugar yields using response surface methodology (RSM). The optimum pressure and solid and enzyme loadings were found as 1500 bar, 1%, and 15 FPU/g dry wheat straw, respectively. The yields obtained at this condition were 82%, 94%, and 65% for glucose, xylose, and ethanol, respectively. High sugar yields implied that microfluidization is an effective pretreatment method for cellulosic ethanol production. On the other hand, low ethanol yield may indicate that the microorganism was sensitive to inhibitory compounds present in the fermentation medium.

Evaluation of hydrogen production by Clostridium strains on beet molasses

Clostridium acetobutylicum DSM 792, C. acetobutylicum DSM 1731 and two newly isolated bacteria defined as the members of genus Clostridium – based on the 16S rRNA analysis and biochemical traits – were characterized with regard to their hydrogen production in media containing increasing beet molasses concentrations. The highest hydrogen yield was observed for C. acetobutylicum DSM 792 with a yield of 2.8 mol H2 mol−1 hexose in medium including 60 g L−1 molasses. This bacterium also produced the maximum amount of hydrogen (5908.8 mL L−1) at the same molasses concentration. A slightly lower hydrogen yield was measured for C. acetobutylicum DSM 1731 (2.5 mol H2 mol−1 hexose) when grown on 40 g L−1 molasses. The new isolates Clostridium roseum C and Clostridium saccharoperbutylacetonicum PF produced hydrogen with yields of 2.0 mol H2 mol−1 hexose at 40 and 60 g L−1 molasses and 2.1 mol H2 mol−1 hexose at 40 g L−1 molasses, respectively.

Purification and characterization of a thermostable cyclodextrin glycosyltransferase from Thermoanaerobacter sp. P4

Cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) from a thermophilic anaerobic bacterium, Thermoanaerobacter sp. P4, was purified by ammonium sulfate precipitation followed by α-cyclodextrin epoxy activated-sepharose 6B column chromatography. Enzyme was purified 141 fold and had the specific activity of 143.8 U/mg proteins. Purification yields after ammonium sulfate precipitation and affinity chromatography were 25.8 and 17.8%, respectively. SDS-PAGE analysis showed that enzyme was purified successfully and had a single band. Molecular weight of the enzyme was determined as 68.7 kDa. The enzyme had optimum cyclization activity at 80 to 90°C and hydrolyzing activity at 90°C and maintained 87 and 95% of these activities at 95°C, respectively. Optimal pH was found as 7.0. It retained full activity at 80°C for 4 h. Enzyme was strongly inhibited by HgSO 4 and AgNO 3 . Addition of 1 mM CaCl 2 increased the enzymatic activity up to 7%. This novel enzyme could be a good candidate for industrial applications according to its characteristic found in the current study. Key words: Cyclodextrin glycosyltransferase, cyclodextrin production, Thermoanaerobacter sp. P4, thermophilic, enzyme purification, enzyme characterization.

Influence of osmotic and metal stresses on nitrogenase activity of cyanobacteria isolated from paddy fields

Samples were collected from paddy fields in Corum-Turk.ye. Nitrogen-free BG-11 medium was used for isolation of nitrogen fixing cyanobacteria. Acetylene reduction technique was used to determine the effects of different chemical agents on the nitrogenase activities of the cyanobacteria, which were identified at the genus level. Nostoc showed the highest nitrogenase activity (0.09 ethylene ƒEl/mg.h) at 50 mM salt concentration. At 60 mM sucrose concentration, Nostoc showed the highest nitrogenase activity (0.08 ethylene ƒEl/mg.h). The highest tolerances for the metals were present in Anabaena (0.006 ethylene ƒEl/mg.h) for iron (20 ppm), Nodularia 0.1 ethylene ƒEl/mg.h (for manganese 20 ppm) and Nostoc 0.96 ethylene ƒEl/mg.h (for zinc 5 ppm) .

THE USAGE OF CARROT POMACE FOR BIOETHANOL PRODUCTION

The lignocellulosic substances such as agricultural wastes are promising feedstocks for bioethanol production. Because they are cost effective, renewable, abundant and not having primary value for food and feed. The current study suggests that improvements in polysaccharide hydrolysis of under-utilized biomass of carrot pomace may find practical use in its conversion to bioethanol by Saccharomyces cerevisiae and Pichia stipitis fermentation. Some important parameters for bioethanol production such as pretreatment procedures (CaO and activated charcoal treatments), nitrogen sources ((NH) 2 SO 4 , soy wheat, cheese whey), and pomace loading amount (15-120 g/L) were optimized in the study. The highest bioethanol production could be achived when the saccharification and fermentation conditions were optimized in order to increase monosaccharide yield and fermentation of both six-carbon and five-carbon monosaccharides. The bioethanol production was 1.9 –fold higher for S. cerevisiae and 4.6 –fold higher for P. stipitis when (NH 4 ) 2 SO 4 was added in addition to the trace nitrogen substances, vitamins and minerals present in carrot pomace. The highest bioethanol production values were obtained as 6.91 and 2.66 g/L in the presence of 120 g/L pomace loading, 1 g/L (NH) 2 SO 4 at the end of 72 hours incubation time at pH 6 by S. cerevisiae and P. stipitis , respectively.

A Thermostable Cyclodextrin Glycosyltransferase from Thermoanaerobacter sp. 5K

Cyclodextrin glycosyltransferase (CGTase) from the thermophilic anaerobe Thermoanaerobacter sp. 5K was purified and characterized. The enzyme was purified with ammonium sulfate precipitation followed by α-CD-bound, epoxy-activated Sepharose 6B affinity chromatography. Molecular weight of the purified enzyme was 70.6 kDa. The enzyme had optimal activity at 80-90°C and retained greater than 90% activity between 75°C and 95°C. Optimal pH activity was observed at 7.0, with at least 50% activity between pH 4.0 and 9.0. It was highly stable at elevated temperature, with no loss of activity after incubation at 80°C for 4 hours or at 90°C for 30 min. Km and Vmax values were 0.222 mg/mL and 0.206 mg β-CD/mL/min, respectively, with soluble starch. Amino acid composition of the enzyme was deduced from the sequence of the cloned CGTase gene. The mature enzyme has a deduced molecular weight of 75.63 kDa and contains residues conserved in the CGTase class of amylase enzymes.