Investigation of the effects of dissolved oxygen concentration, aeration and agitation on the morphology and rheology in submerged fungal fermentation

Thesis (Master)--Izmir Institute of Technology, Food Engineering, Izmir, 2007Includes bibliographical references (leaves: 70-77)Text in English; Abstract: Turkish and Englishxi, 80 leavesThe effects of pH, agitation speed, dissolved oxygen tension (DOT) and aeration, significant in common fungal fermentations, on the production of polygalacturonase (PG) enzyme and their relation to morphology and broth rheology were investigated in a batch bioreactor using Aspergillus sojae which has no available literature report on the pectinase production. All four factors were effective on the response parameters under study. An uncontrolled pH increased biomass and PG activity by 27% and 38%, respectively compared to controlled pH (pH 6). pH did not significantly affect the broth rheology but created an impact on the pellet morphology. Similarly, the maximum biomass obtained at 500 rpm and at 30h was 3.27 and 3.67 times more than at 200 and 350 rpm, respectively. The maximum enzyme productivity of 0.149 U ml-1 h-1 was obtained at 200 rpm. Non . Newtonian and pseudoplastic broth rheology was observed at 500 rpm agitation speed. Furthermore, a DOT range of 30-50% was essential for maximum biomass formation, whereas only 10% DOT was required for maximum PG synthesis. Non . Newtonian shear thickening behavior (n>1.0) was depicted at DOT levels of 10% and 30%, whereas, non-Newtonian shear thinning behavior (n<1.0) was dominant at 50% DOT. When 2.5 l/min aeration experiment was investigated detaily; it was determined that at about 21st hour, polygalacturonase production approaches its maximum (1.49 U) and pellets are smaller, high in number. At 48th hour; polygalacturonase production declines to zero, biomass reaches its maximum and pellets are big (average pellet size is 1.94±0.58 mm) and fluffy with compact centers. At the end of fermentation (96.hour), fermentation medium is close to Newtonian. The overall fermentation duration (50-70h) was considerably shorter as opposed to common fungal fermentations revealing the economic feasibility of this particular process. As a result this study not only introduced a new strain with a potential of producing a highly commercially significant enzyme but also provided certain parameters significant in the design and mathematical modelling of fungal bioprocesses

Investigation of the effects of dissolved oxygen concentration, aeration and agitation on the morphology and rheology in submerged fungal fermentation

Thesis (Master)--Izmir Institute of Technology, Food Engineering, Izmir, 2007Includes bibliographical references (leaves: 70-77)Text in English; Abstract: Turkish and Englishxi, 80 leavesThe effects of pH, agitation speed, dissolved oxygen tension (DOT) and aeration, significant in common fungal fermentations, on the production of polygalacturonase (PG) enzyme and their relation to morphology and broth rheology were investigated in a batch bioreactor using Aspergillus sojae which has no available literature report on the pectinase production. All four factors were effective on the response parameters under study. An uncontrolled pH increased biomass and PG activity by 27% and 38%, respectively compared to controlled pH (pH 6). pH did not significantly affect the broth rheology but created an impact on the pellet morphology. Similarly, the maximum biomass obtained at 500 rpm and at 30h was 3.27 and 3.67 times more than at 200 and 350 rpm, respectively. The maximum enzyme productivity of 0.149 U ml-1 h-1 was obtained at 200 rpm. Non . Newtonian and pseudoplastic broth rheology was observed at 500 rpm agitation speed. Furthermore, a DOT range of 30-50% was essential for maximum biomass formation, whereas only 10% DOT was required for maximum PG synthesis. Non . Newtonian shear thickening behavior (n>1.0) was depicted at DOT levels of 10% and 30%, whereas, non-Newtonian shear thinning behavior (n<1.0) was dominant at 50% DOT. When 2.5 l/min aeration experiment was investigated detaily; it was determined that at about 21st hour, polygalacturonase production approaches its maximum (1.49 U) and pellets are smaller, high in number. At 48th hour; polygalacturonase production declines to zero, biomass reaches its maximum and pellets are big (average pellet size is 1.94±0.58 mm) and fluffy with compact centers. At the end of fermentation (96.hour), fermentation medium is close to Newtonian. The overall fermentation duration (50-70h) was considerably shorter as opposed to common fungal fermentations revealing the economic feasibility of this particular process. As a result this study not only introduced a new strain with a potential of producing a highly commercially significant enzyme but also provided certain parameters significant in the design and mathematical modelling of fungal bioprocesses

Bamya müsilajının termo-reolojik özelliklerinin belirlenmesi

Bu tez çalışmasında, beslenme ve sağlık açısında değerli bir ürün olan bamya sebzesinde bulunan müsilaj kısmı ultrason destekli ekstraksiyonla elde edilmiş, kimyasal ve fiziko kimyasal yöntemlerle bu polisakkarit ekstraktının yapısal, ısıl ve reolojik özellikleri belirlenmiştir. Isıl özelliklerden camsı geçiş sıcaklığı, erime sıcaklığı ile faz değişim entalpilerinin belirlenmesinde diferansiyel tarama kalorimetresi kullanılmıştır. Değişik katı/çözgen oranlarında (1:10, 1:25, 1:30, 1:50) 5 ve 30 dakikalık ekstraksiyon süreleri ekstraksiyona tabi tutularak elde edilen örneklerin camsı geçiş sıcaklıkları ortalama 50oC civarında, erime sıcaklıkları ise 166 – 170oC aralığında bulunmuştur. Bamya polisakkaritlerinin termal stabilitesini analiz etmek için termogravimetri (TG) ve diferansiyel termogravimetri (DTG) teknikleri kullanılmıştır ve sonuçlar bamya müsilajının termal stabilitesinin iyi olduğunu göstermiştir. Gıdaların ısıl iletkenlik ölçümünde daha önce hiç kullanılmamış olan 3ω yöntemiyle ısıl iletkenlik ölçümü yapılmış ve bamya polisakkaritinin ısıl iletkenlik değerlerinin sudan çok farklı olmadığı tespit edilmiştir. Ekstraktlardaki bileşim hakkında detaylı bilgi veren, polisakkaritlerin içerdiği bağları aydınlatmaya yarayan, farklı bamya/distile su oranları ve farklı ekstraksiyon süreleri sonucu elde edilen polisakkaritlerin karakterizasyonu amacıyla FTIR analizleri yapılmıştır. Bamyanın galaktoz, ramnoz ve galakturonik asit olan ana bileşenleri FTIR analiz spektrumunda gözlemlenebilmiştir. Çalışmada farklı bamya/distile su oranında (1:10 ve 1:30) ekstrakte edilen polisakkaritlerin farklı konsantrasyonlardaki (%1, 2, 3, 4; w/v) çözeltilerinin, değişik sıcaklıklardaki (10, 20, 40, 60, 80oC) akış davranış özellikleri incelenmiştir. Reolojik özellikler Power Law (Üssel) modele göre analiz edilmiş ve parametreler hesaplanmıştır. Bamya polisakkaritlerinin Newton dışı psödoplastik akış karakteristiğini gösterdiği gözlenmiştir. Akış davranışı indeksinin 0,234 ile 0,947 arasında, kıvam katsayısının ise 0,00437 ile 0,2445 Pa.sn arasında değiştiği görülmüştür. Kıvam katsayısı (K), ve akış davranış indeksi (n) sıcaklık arttıkça azalmıştır. Aynı şekilde K değeri konsantrasyon arttıkça artmaktadır. Akış davranış indeksi (n) değerleri ise konsantrasyon ile düzenli bir davranış göstermemiştir. Bamya polisakkarit örneklerinin görünür viskozitelerine sıcaklığın etkisi 10 – 80oC arasında beş farklı sıcaklıkta incelenmiştir. Ölçümler sonunda kıvam katsayısının sıcaklıkla değişim grafiği çizilmiş ve kıvam indeksine sıcaklığın etkisi Arrhenius denklemi ile modellenmiştir. 1:10 ve 1:30 katı/çözgen oranına sahip iki örnekte de konsantrasyon arttıkça aktivasyon enerjisi artmıştır ve 1:10, %4 konsantrasyon için en yüksek aktivasyon enerjisi değerine ulaşılmıştır (275,8434 kj/mol). Sonuç olarak elde edilen bu polisakkaritler, yapılan analizler sayesinde yapışkan ve gamsı yapısı sayesinde kıvam arttırıcı olarak gıda sanayisinde, atıklarının yüksek adsorbsiyon kapasitesine sahip olması özelliği ile atık su arıtma sistemlerinde, emülsiyonlaştırıcı ve süspanse edici ajan olarak farmasotik gibi alanlarda kullanımı yaygınlaştırılabilecektir.In this thesis, the mucilage portion of the okra which is a valuable product in terms of nutrition and health was obtained by ultrasound assisted extraction, and the structural, thermal and rheological properties of this polysaccharide extract were determined by chemical and physicochemical methods. In the determination of phase change enthalpy by investigating the glass transition temperature and enthalpy, the differential scanning calorimetry was used. At various solid / solvent ratios (1:10, 1:25 1:30 1:50) and extraction times of 5 and 30 minutes, the glass transition temperatures of the samples were found to be approximately 50oC and melting temperatures in the range of 166-170°C. Thermogravimetry (TG) and differential thermogravimetry (DTG) techniques were used to analyze the thermal stability of Okra polysaccharides and the results showed that the thermal stability of the okra mucilage was good. Thermal conductivity was measured by 3 ω method and it was determined that the thermal conductivity values of okra polysaccharide were not much different from water. FTIR analysis was carried out for the characterization of polysaccharides obtained by different extraction times and different rates of okra / distilled water, which provide detailed information about the composition of the extracts, to illuminate the bonds of polysaccharides. The main components of okra which were galactose, rhamnose and galacturonic acid can be observed in the FTIR analysis spectrum. In the study, flow behavior characteristics of the polysaccharides extracted at different okra / distilled water ratio (1:10 and 1:30), at different concentrations of polysaccharides (1%, 2, 3, 4; w / v) of the extracts at different temperatures (10, 20, 40, 60, 80oC) were investigated. The rheological properties were analyzed according to the Power Law model and the parameters were calculated. It was observed that okra polysaccharides showed non-Newton pseudoplastic flow characteristics. Flow behavior index varied between 0.234 and 0.947, and the consistency coefficient varied between 0.00437 and 0.2445 Pa.sn. The consistency coefficient (K), and the flow behavior index (n) decreased as the temperature increased. In the same way, the K value increases as the concentration increases. The flow behavior index (n) values did not show a regular behavior with concentration. The effect of temperature on apparent viscosities of okra polysaccharide samples was investigated at five different temperatures between 10 – 80oC. At the end of the measurements, a graph of change of consistency coefficient with temperature was drawn and the effect of temperature on the consistency index was modeled by the Arrhenius equation. In two samples with a 1:10 and 1:30 solid / solvent ratio, the activation energy increased as the concentration increased, and the highest activation energy value was reached for the 1:10, 4% concentration (275,8434 kj / mol). As a result, these polysaccharides can be used in the food industry as a thickening agent due to their adhesive and viscous structure and in the wastewater treatment systems with their high adsorption capacity, and their use as emulsifier and suspension agent in the fields such as pharmaceuticals