Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Subject: search.filters.subject.Lactic acid

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  • Article
    Citation - WoS: 23
    Citation - Scopus: 27
    Use of Deep Eutectic Solvents in the Enzyme Catalysed Production of Ethyl Lactate
    (Elsevier, 2019) Arıkaya, Azime; Arıkaya, Azime; Ünlü, Ayşe Ezgi; Takaç, Serpil; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The use of deep eutectic solvents (DESs) in the lipase-catalysed esterification of lactic acid with ethanol was explored by screening several DESs. Choline chloride:glycerol (1:2) was the most effective DES and provided 28.7% yield of ethyl lactate under the following conditions: 10% (v/v) of water content in DES, 3 M of initial lactic acid concentration, 5 M of initial ethanol concentration, 30 mg/mL of enzyme concentration, 50 degrees C temperature and 200 rpm agitation rate. Individual and combined effects of the reaction medium components on the enzyme activity were investigated and it was discovered that DES stimulated the enzyme activity while reactants inhibited it. A kinetic model that obeys the Ping-Pong Bi-Bi mechanism with ethanol inhibition was suggested. The kinetics parameters were determined as r(max) = 0.401 mol/L h, the Michaelis constants K-A = 1.657 mol/L and K-B = 0.799 mol/L, the inhibition constant K-iB = 0.156 mol/L. The model reasonably predicted the experimental data. The activation energy was found to be 43.28 kJ/mol. Mass transfer limitations in the reaction medium were negligible. The results are promising for further studies that will research on the use of green solvents in enzyme catalysed lactic acid esterification reactions.
  • Article
    Citation - WoS: 51
    Citation - Scopus: 55
    Kinetic Modelling of Lactic Acid Production From Whey by Lactobacillus Casei (nrrl B-441)
    (John Wiley and Sons Inc., 2006) Altıok, Duygu; Tokatlı, Figen; Harsa, Hayriye Şebnem; Tokatlı, Figen; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The biomass growth, lactic acid production and lactose utilisation kinetics of lactic acid production from whey by Lactobacillus casei was studied. Batch fermentation experiments were performed at controlled pH and temperature with six different initial whey lactose concentrations (9-77 g dm-3) in a 3 dm3 working volume bioreactor. Biomass growth was well described by the logistic equation with a product inhibition term. In addition, biomass and product inhibition effects were defined with corresponding power terms, which enabled adjustment of the model for low- and high-substrate conditions. The Luedeking-Piret equation defined the product formation kinetics. Substrate consumption was explained by production rate and maintenance requirements. A maximum productivity of 2.5 g dm-3 h-1 was attained with an initial lactose concentration of 35.5 g dm-3.
  • Article
    Citation - WoS: 29
    Citation - Scopus: 32
    Optimization of Lactic Acid Production From Whey by L Casei Nrrl B-441 Immobilized in Chitosan Stabilized Ca-Alginate Beads
    (John Wiley and Sons Inc., 2005) Göksungur, Mehmet Yekta; Gündüz, Meltem; Harsa, Hayriye Şebnem; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The production of lactic acid from whey by Lactobacillus casei NRRL B-441 immobilized in chitosan-stabilized Ca-alginate beads was investigated. Higher lactic acid production and lower cell leakage were observed with alginate-chitosan beads compared with Ca-alginate beads. The highest lactic acid concentration (131.2 g dm-3) was obtained with cells entrapped in 1.3-1.7 mm alginate-chitosan beads prepared from 2% (w/v) Na-alginate. The gel beads produced lactic acid for five consecutive batch fermentations without marked activity loss and deformation. Response surface methodology was used to investigate the effects of three fermentation parameters (initial sugar, yeast extract and calcium carbonate concentrations) on the concentration of lactic acid. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar, yeast extract and calcium carbonate concentrations had a strong linear effect on lactic acid production. The maximum lactic acid concentration of 136.3 g dm-3 was obtained at the optimum concentrations of process variables (initial sugar 147.35 g dm-3, yeast extract 28.81 g dm-3, CaCO3 97.55 g dm-3). These values were obtained by fitting of the experimental data to the model equation. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in lactic acid production using alginate-chitosan-immobilized cells.