Browsing by Author "Keskinler, Bülent"
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Item Batch fermentation of succinic acid from cheese whey by Actinobacillus succinogenes under variant medium composition(Springer, 2021-07-29) Omwene, Philip Isaac; Yağcıoğlu, Meltem; Öcal-Sarihan, Zehra Betül; Ertan, Fatma; Keris-Sen, Ülker Diler; Karagunduz, Ahmet; Keskinler, BülentBio-based succinic acid production has attracted global attention since its consideration as a potential replacement to petroleum-based platform chemicals. This study used three different CO2 sources, namely NaHCO3, K2CO3 and MgCO3 for fermentation of succinic acid (SA) by Actinobacillus succinogenes under three distinct substrate conditions i.e. lactose, whey and whey devoid of any supplements. Batch experiments were performed in both anaerobic flasks and 5L benchtop fermenter. SA fermentation in anaerobic flasks was unfettered by supplementary nutrients. However, fermentation in the benchtop fermenter devoid of supplementary nutrients resulted into 42% reduction in SA yield as well as lower SA productivities. Furthermore, a significant reduction of cell growth occurred in anerobic flasks at pH < 6.0, and complete termination of bacterial activity was noted at pH < 5.3. The highest SA titer, yield and productivity of 15.67 g/L, 0.54 g/g and 0.33 g/L/h, respectively, was recorded from whey fermentation with MgCO3. The present study further highlights significant inhibitory effect of K2CO3 buffered medium on Actinobacillus succinogenes. Thus, we can claim that environmental pollution as well as costs of SA production from whey can be reduced by leveraging on whey residual nutrients to support the activity of Actinobacillus succinogenes.Item Conforming to agricultural water reuse criteria: wastewater recovery by electrooxidation integrated with nanofiltration/reverse osmosis(Springer Nature, 2023-02-21) Çiftçioğlu‑Gözüaçık, Bengisu; Omwene, Philip Isaac; Ergenekon, Sinem Merve; Karagunduz, Ahmet; Keskinler, BülentIn this study, two membrane configurations were investigated for water recovery in order to determine the potential for quality irrigation water production from alkaloid industry wastewater. In the first configuration, electrooxidation (EO) was used as a pretreatment before the NF90/BW30 units. In the second configuration, a single-pass, two-stage system consisting of NF4 and NF90/BW30 membranes was applied by replacing the EO unit with NF4. The initial and final fluxes in the single-pass two-stage system with NF4 and NF90 were calculated as 10.2 Lm− 2h− 1 and 5.4 Lm− 2h− 1, respectively. Initial fluxes for the NF4 + BW30 and EO + BW30 combinations were 9.4 Lm− 2h− 1 and 3.2 Lm− 2h− 1, respectively. Increasing the current density from 256 to 768 A/m2 caused the specific energy consumption (SEC) to increase from 10.26 to 15.84 kWh/kg COD. Scanning Electron Microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used for membrane autopsies. Compliance with the criteria for agricultural reuse of recovered water was evaluated based on four key parameters: salinity, pathogens, nutrients, and heavy metals. The combination of electrooxidation and membrane treatments enabled simultaneous disinfection, reduction of salinity and heavy metals to comparable agricultural water reuse criteria.Item Novel chromatographic purification of succinic acid from whey fermentation broth by anionic exchange resins(Springer Nature, 2022-11-09) Omwene, Philip Isaac; Öcal, Zehra Betül; Yağcıoğlu, Meltem; Karagündüz, Ahmet; Keskinler, BülentReplacement of the petroleum-based refineries with the biorefinery is regarded as an essential step towards a “zero” waste (circular) economy. Biobased succinic acid (SA) is listed by the United States Department of Energy among the top ten chemicals with the potential to replace chemicals from petroleum synthesis with renewable sources. Purification of biobased succinic acid from fermentation by-products such as alcohols, formic acid, acetic acid and lactic is a major drawback of fermentative SA production. This study addresses this issue through a novel chromatographic separation using three distinct anionic resins: Amberlite IRA958 Cl (strong base anion exchange resin), Amberlite HPR 900 OH (strong base anion exchange resin) and Amberlyst A21 (week base anion exchange resin). The influence of process variables such as flow rate (0.18 BV/h, 0.42 BV/h and 0.84 BV/h), eluent concentration (1%, 5% and 10% HCl) and temperature (20, 30 and 40 °C) were investigated. The results indicated SA separation efficiency of 76.1%, 69.3% and 81.2% for Amberlyst A21, Amberlite HPR 900 OH and Amberlite IRA958 Cl, respectively. As the regenerant HCl concentration increased from 1 to 10%, calculated succinic acid separation efficiencies decreased from 80.3 to 70.7%. Notably, as the regenerant strength increased from 1 to 10%, the total amount of organic acids desorbed from the resin sharply increased. At operation temperatures of 20, 30 and 40 °C, SA separation efficacies were 81.2%, 73.9% and 76.4%, respectively. The insights from this study will be of great value in design of chromatographic separation systems for organic acids.Item Recovery of succinic acid from whey fermentation broth by reactive extraction coupled with multistage processes(Science Direct, 2020-06) Omwenea, Philip Isaac; Yagcioglu, Meltem; Sarihan, Zehra Betül Ocal; Karagunduz, Ahmet; Keskinler, BülentFermentative production of succinic acid (SA) from renewable resources such as whey is environmentally sustainable compared to petroleum-based synthesis. However, a major drawback of fermentation is the concurrent production of SA with byproducts such as lactic acid (LA), formic acid (FA) and acetic acid (AA). Therefore, appropriate downstream SA recovery and purification steps are significant in ensuring sustainable SA production. In this study, SA was fermented by Actinobacillus succinogenes and recovered in an integrated process consisting of ultrafiltration, vacuum distillation and reactive extraction. The extractant used was tri-n-octylamine (TOA) with 1-octanol as a diluent for both liquid-liquid (LLE) extraction and supported liquid membrane (SLM). The produced SA titer and yield was 11.16 g/L and 0.44 g/g, respectively. The steady state ultrafiltration permeate flux ranged from 31.18 to 33.42 L/m2h, and complete decolorization of the fermentation broth was achieved with 10 % (w/v) of powdered activated carbon. The extraction efficiency for LLE was 51.5 %, whereas SLM achieved 57.3 % recovery. SA exhibited transport and permeability coefficient of 0.00697 h−1 (R2 > 0.92) and 0.08605 cm h−1, respectively. Extraction of SA tremendously decreased as the aqueous pH was increased from 2 to 5. In SLM, initial SA flux was calculated as 9.65 g/m2h and doubled that of lactic acid. Selective extraction of only SA was not achieved; however, residue biological material and macromolecular substances were effectively removed. Herein, we clearly demonstrated that process integration applied in reactive extraction is a promising approach for recovery of SA from fermentation broth.