Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 TechnologyLactic 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.Master Thesis Structural Changes of Gliadins During Sourdough Fermentation as a Promissing Approach To Gluten-Free Diet(Izmir Institute of Technology, 2010) Kömen, Gökçen; Harsa, Hayriye Şebnem; Harsa, Hayriye Şebnem; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyGluten intolerance, celiac disease, is an autoimmune disease caused by the ingestion of gluten proteins and the only treatment is the strict gluten-free diet which results in a mucosal recovery. At this point, the variety, availability and low price of gluten-free products on the market are of great importance. Sourdough is a traditional fermented semi-product that contains lactic acid bacteria (LAB). LAB are capable of metabolizing proteins and peptides with their proteolytic enzymes. It is predicted that gluten proteins are able to be hydrolyzed with the help of this proteolytic mechanisms and also by the wheat proteolytic enzymes. the help of this proteolytic mechanisms and also by the wheat proteolytic enzymes. gliadins involved in gluten intolerance during sourdough fermentation with selected LAB. First, sourdough fermentation with selected Lactobacillus strains was accomplished. As a control, dough with no inoculation and chemically acidified dough were prepared. During 48 h of fermentation, changes in pH, acidity, LAB concentration and free amino nitrogen content were investigated. SDS-PAGE, 2-D electrophoresis and RP-HPLC were applied to prolamins extracted from each sourdough sample taken at definite time intervals. The results showed that the inoculated LAB adapted to the dough environment and as they grew, a decrease in pH, and an increase in acidity and free amino nitrogen were observed. According to SDS-PAGE, 2-D electrophoresis and RP-HPLC results, some modifications in the protein patterns were observed in the inoculated doughs. The same alterations occurred in control and chemically acidified doughs, but not as fast as inoculated ones.