Otimização da produção de óleo microbiano por Umbelopsis isabellina e microencapsulação pelo método de gelificação iônica externa

Abstract

Filamentous fungi such as Umbelopsis isabellina have emerged as a biotechnological alternative for obtaining oils rich in monounsaturated and polyunsaturated fatty acids, which are important nutrients for the regulation of physiological processes involved in the development and maintenance of human health. Due to their chemical characteristics, these oils are highly susceptible to lipid oxidation and microencapsulation can be a useful tool to increase the lipid stability of the microbial oil. Thus, the aim of this study was to optimize the production of microbial oil by Umbelopsis isabellina and microencapsulate this oil by the external ionic gelation method. Initially, using an orbital shaker, the parameters of the culture medium (yeast extract, peptone, and sucrose) and the parameters of the fermentation process (stirring rate, temperature and pH) were optimized in order to produce lipids and PUFAs through planning of the Plackett–Burman (BP) type. Afterwards, the scale-up to a STR bioreactor was carried out and, additionally, the agitation and aeration rates were evaluated using a central composite rotational design (DCCR). After completing all optimization steps, the final lipid yield was 36.58% of which 14.88% were PUFA. Fifteen fatty acids were identified, the majority being: oleic acid (47%), palmitic acid (27%), linoleic acid (11%) and γ-linolenic acid (5%). The second stage of the study aimed to microencapsulate the microbial oil by the external ionic gelation method and microcapsules had an average diameter of 105 µm and the encapsulation efficiency was 80%. In this step, the oxidative stability of the free and microencapsulated oil was also evaluated over the storage time, varying temperature, and luminosity. The ionic gelation method was suitable to microencapsulate the microbial oil as it did not alter the lipid oxidation markers (peroxide index and formation of conjugated dienes). The combination of microencapsulation and refrigerated storage was the condition that presented the greatest lipid stability during the evaluated storage time. In addition, microcapsules containing microbial oil stored at refrigerated temperature showed the smallest variation in the content of saturated, monounsaturated, and polyunsaturated fatty acids during storage when compared to microcapsules stored at room temperature or free oil stored at different temperatures. Based on the data presented, it is possible to conclude that the fungus Umbelopsis isabellina, under optimized conditions, can produce an oil rich in unsaturated fatty acids and with good yield, and its production scale can be expanded for industrial purposes. The microbial oil produced can be microencapsulated, without prejudice to its constitution, by the external ionic gelling method and that microencapsulation is an effective tool to prolong lipid stability, reducing its reactions to external environmental factors, thus facilitating its use in the food industry, and allowing the microbial oil produced by the fungus Umbelopsis isabellina to have the potential to be used in the development of food or nutraceutical ingredients.