Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Subject: search.filters.subject.Lactic acid

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  • Master Thesis
    L[+]-Lactic Acid Purification From Fermentation Broth Using Ion Exchange Resins
    (Izmir Institute of Technology, 2002) Polat, Zelal; Harsa, Hayriye Şebnem; Harsa, Hayriye Şebnem; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Lactic acid exists in two optically active form, D(-) and L(+)-lactic acid. It has been used in food, leather, textile, pharmaceutical and cosmetic industries. Moreover, L(+)-lactic acid constitutes the raw material for the production of poly-L-lactic acid which is used in biomedical applications.The aim of this study was to recover and purify the microbially produced L(+)-lactic acid from the fermentation media efficiently and economically. Among the various downstream operations, ion exchange chromatography was used since it is highly selective and yields a low cost product recovery within a short period of time. The additional goals were to investigate the end product purity, to obtain new data on the adsorption/desorption behaviours of lactic acid and to investigate the applicability of the system for industrial usage. In this project, Lactobacillus casei NRRL B-441 was used for the production of L(+)-lactic acid from whey by a 12 hours fermentation process at pH 5.5 and 37 oC. The product concentration was 50 g/l with 100% L(+)-lactic acid content. Then, a suitable resin with high sorption capacity and rapid equilibrium behavior was selected. The selected resin was Dowex marathon WBA, a weakly basic anion exchanger in OH form. It reached the equilibrium state in 15 minutes. The batch sorption experiments were done at pH 7.0 and 30 oC and sampling was continued for 20 hours. Furthermore, the effect of temperature and pH was investigated and their influence was found to be unimportant. All the adsorption/desorption experiments were applied both to model lactic acid and to biomass free fermentation broth. The ion exchange equilibria of lactic acid and L(+)-lactic acid in fermentation broth on Dowex marathon WBA were explained by the Langmuir isotherm. The maximum exchange capacity (qm) for model lactic acid was 0.25 g La/g wet resin, while L(+)-lactic acid in fermentation broth has a qm value of 0.04 g La/g wet resin. The equilibrium loading and exchange efficiency of L(+)-lactic acid in fermentation broth were reduced as a result of competition by other ionic species. The competing ions inhibit the binding of L(+)-lactic acid to the free sites of ion exchanger. Moreover, column operations were applied to recover sorbed lactic acid from the ion exchanger. 2.0 M HCl was found to be a suitable eluting agent to recover the bound L(+)-lactic acid with a flowrate of 1 ml/min at ambient temperature. About 95 % of bound L(+)-lactic acid was recovered from Dowex marathon WBA.
  • Master Thesis
    Lactic Acid Production by Lactobacillus Casei Nrrl B-441 Immobilized in Chitosan Stabilized Ca-Alginate Beads
    (Izmir Institute of Technology, 2005) Gündüz, Meltem; Harsa, Hayriye Şebnem; Harsa, Hayriye Şebnem; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Having two optically active forms, D(-) and L(+) lactic acid has long been used in the food, chemical, textile, pharmaceutical and other industries. 90 % of the worldwide production of lactic acid is by bacterial fermentation. Recently, there is an increasing interest in the production of L(+) lactic acid, since it is a potential substrate for polylactic acid that is biocompatible and can be used for medical purposes. Whey, which is a by-product of dairy industry, contains approximately 5 % (w/v) lactose. Since whey has a high BOD content, it possesses serious environmental problems. Whey lactose is a good substrate for lactic acid bacteria and can be used for L(+) lactic acid fermentations. This study focuses on the production of lactic acid from whey by Lactobacillus casei NRRL B-441 immobilized in chitosan stabilized Ca-alginate beads. Higher lactic acid production and lower cell leakage were observed with alginate-chitosan beads compared with Ca-alginate beads. The highest lactic acid (131.2 g/l) was obtained with cells entrapped in 1.3-1.7 mm alginate-chitosan beads prepared from 2 % Na-alginate. acid production and lower cell leakage were observed with alginate-chitosan beads compared with Ca-alginate beads. The highest lactic acid (131.2 g/l) was obtained with cells entrapped in 1.3-1.7 mm alginate-chitosan beads prepared from 2 % Na-alginate. The gel beads produced lactic acid for 10 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. No previous work has used statistical analysis in determining the interactions among these variables in lactic acid production by immobilized cells. 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 strong linear effects on lactic acid production. Maximum lactic acid concentration of 136.3 g/l was obtained at the optimum levels of process variables (initial sugar concentration.147.35 g/l, yeast extract concentration. 28.81 g/l, CaCO3 concentration.97.55 g/l). 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.
  • Master Thesis
    Kinetic Modelling of Lactic Acid Production From Whey
    (Izmir Institute of Technology, 2004) Altıok, Duygu; Tokatlı, Figen; Tokatlı, Figen; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Lactic acid is a natural organic acid, which is used in pharmaceuticals, chemical, textile and food industries. Since only L(+) lactic acid is found in normal human metabolism, the microbial production of L(+) lactic acid has great interest in recent years. Use of whey lactose to produce lactic acid by fermentation process is favourable due to the low cost of whey and its high organic matter content. Whey is suitable medium for some fermentations. However, its high lactose content makes it a potential environmental pollutant. The disposal problem of this pollutant could be overcome by utilization of whey lactose in the lactic acid production.The aim of this study was to develop a kinetic model for lactic acid productionfrom whey by Lactobacillus casei, which is a homofermentative lactic acid bacteria andcapable of producing L(+) lactic acid. Within this context, several batch fermentationexperiments in fermenter were performed at 37 C and pH 5.5. Seed culture that was produced in shake flask fermentations was used as the inoculum for the fermenter.Before the fermentation experiments, some of the proteins in whey were denatured by heat treatment and separated by centrifugation. This treatment decreased the protein amount from 11.15 % to 5.2 % in whey powder. The lactic acid production was associated with the biomass growth up to a certain time, but then a non-growth associated lactic acid production was observed in most of the fermentations except for the 9.0 g l-1 initial substrate fermentation run, where all the substrate was utilized when the stationary phase was attained. The maximum theoretical productivity was obtained as 2.4 g lactic acid l-1 h-1 in the fermentation with S0 equals to 35.5 g l-1. The kinetic parameters were obtained from different fermentation runs. mmax and KS were found as 0.265 h-1 and 0.72 g l-1, respectively. The average product yield coefficient, YPS, was determined as 0.682 g lactic acid (g lactose)-1.The modified form of logistic equation with product inhibition term for biomassThe modified form of logistic equation with product inhibition term for biomass growth, Luedeking and Piret equation for product formation and substrate utilization considering the consumption of substrate for product formation and maintenance, described most of the fermentation experiments in this study with high accuracy (SSE range was 0.0804-0.1531). The toxic powers in these inhibition terms, h and f, made the model applicable for the fermentation experiments with low and high initial substrate concentrations. In case of high initial substrate concentration fermentation (S0. 95.7 g l-1), the same model explains only the exponential phase of biomass and its product formation eventhough the substrate consumption is predicted very well.product formation eventhough the substrate consumption is predicted very well.