Gıda Atıklarından Çeşitli Ön İşlemlerle Elde Edilen Besin Ortamlarında Rhodotorula glutinis Mayası İle Β-Karoten Üretiminin İncelenmesi

Abstract

In this thesis, β-carotene production was carried out with Rhodotorula glutinis yeast in the growth media including sugars obtained by two consecutive steps: Hot water extraction of orange peel, grape pomace and carrot pomace wastes, which are formed in large quantities as waste in the food industry and are generally disposed of without valorization and acidic hydrolysis of the remaining pulp after extraction. In the first part of the study, the sugars included in the untreated (wet) and the pretreated (dried, autoclaved, freezed) orange, grape and carrot wastes were obtained with hot water extraction. Here, the effects of food waste characteristics, applied pretreatment, particle size range and solid/liquid ratio on the total concentration and yield of sugars transferred to the water were investigated. The highest sugar concentrations were obtained by the hot water extraction of untreated (wet) grape pomace in the puree form and dried grape pomace in the powder form as 61.2 g TİŞ/L and 60.7 g TİŞ/L, respectively, at a solid/liquid ratio of 100 g/L. In the following step of the study, the effect of varying initial glucose concentration in the synthetic growth media and the effects of change in particle size range and solid/liquid ratio (initial total reducing sugars, TRS) in the growth media obtained by the hot water extraction of untreated and dried orange, grape and carrot wastes on β-carotene production characteristics of R. glutinis were investigated. Microbial growth and β-carotene production enhanced with the increasing initial glucose concentration up to 100 g/L in the synthetic growth media; however, both values decreased at 150 g/L of initial glucose concentration due to substrate inhibition. Microbial growth and β-carotene production increased with the increasing solid/liquid ratio in the growth media obtained by the hot water extraction of all wastes. While the highest β-carotene concentration was found to be 451.4 mg/L in the synthetic growth medium containing glucose; it was determined as 5988.6 mg/L in the growth medium obtained by the hot water extraction of untreated (wet) grape pomace at a solid/liquid ratio of 100 g/L. It has been observed that, microbial growth in the synthetic growth media at varying glucose concentrations between 5-100 g/L and in the natural growth media which were obtained by the hot water extraction of untreated (wet) and dried orange peel, grape pomace and carrot pomace wastes at varying solid/liquid ratios between 10-100 (at varying TIS concentrations), fit the Monod model very well. In the last part of the study, β-carotene production studies from R. glutinis were carried out in the growth media including reducing sugars, which were obtained with the acid hydrolysis of the hot water extraction residue of 100 g/L dried pulpy orange peel, seedless grape pomace and carrot pomace. After the hot water extraction process of 100 g dry waste/L of pulped orange peel, seedless grape pomace and carrot pomace wastes, 70%, 72% and 62% reduction in the mass of the wastes was observed, respectively. In addition, total waste mass decreased by 85.3%, 80.2% and 70.2% for each 100 g/L dry food waste, respectively, after the acid hydrolysis of the extraction residues. Sugar concentrations obtained with acid hydrolysis of pulpy orange peel, seedless grape pomace and carrot pomace extraction residues were determined as 10.1 g/L, 6.7 g/L and 10.8 g/L, respectively. The highest β-carotene concentration of 370.0 mg/L was obtained with R. glutinis growing in the medium obtained by acid hydrolysis of the extraction residues of orange peels. R. glutinis produced 1407.1 mg/L and 370.0 mg/L β-carotene in the medium obtained with the extraction of 100 g/L dried pulpy orange peel and in the medium obtained with the acid hydrolysis of its 30 g/L extraction residue, respectively. Hence, total β-carotene production enhanced by 26% to 1777.1 mg/L. R. glutinis produced 3125.7 mg/L and 153.9 mg/L β-carotene in the medium obtained with the extraction of 100 g/L dried pulpy orange peel and in the medium obtained with the acid hydrolysis of its 28 g/L extraction residue, respectively. Hence, total β-carotene production enhanced by 4.9% to 3279.6 mg/L. R. glutinis produced 2245.7 mg/L and 193.8 mg/L β-carotene in the medium obtained with the extraction of 100 g/L dried pulpy orange peel and in the medium obtained with the acid hydrolysis of its 38 g/L extraction residue, respectively. Hence, total β-carotene production enhanced by 8.6% to 2439.5 mg/L. In this study, for first time in the literature, β-carotene, a high value-added product was produced by the valorization of the food wastes, the product yield was increased with two consecutive processes of extraction with hot water and acidic hydrolysis, and an important contribution was made to the zero waste approach by reducing the residual waste biomasses in significant amounts.