Lipases are enzymes that can be secreted by several microorganisms, making interesting the biodiversity exploration for searching new microorganisms able to produce these enzymes. Many agro-industrial residues can be used as potential substrates for production of enzymes. The main objective of this work was the isolation and screening of microorganisms with potential to produce lipases. Among 24 fungi, five were selected as good lipase producers using tributyrin on agar plates and solid state fermentation of soybean bran. Two of them were isolated from soil samples, another two from soybean bran, and one from dairy products. These fungi were identified by microcultivation technique as from Penicillium and Aspergillus genera. Through random amplified polymorphic DNA technique, the most promising strains could be genetically discriminated, selecting two fungi as good lipase producers but genetically different. One isolated from soybean bran could hydrolyze efficiently triglycerides with fatty acids with different chain length. Another isolated from dairy products was only effective to hydrolyze triglycerides with long-chain fatty acids. Two distinct groups could be verified by means of this technique, comprising the most productive strains and the lowest or nonproductive ones in terms of hydrolytic activity.

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The main objective of this work was the optimization of the lipase production by a newly isolated Penicillium sp. in supplemented soybean meal, considering a fixed C/N ratio (6.11). The kinetic behavior of lipase production was also evaluated, quantifying activity at different pH. The production of the enzyme was maximum using a substrate particle size between 1 and 2 mm and inoculum concentration of 2✕10 8 spores • g -1 , at 20°C. Lipase activities of about 200 U • g -1 at pH 4.0 were obtained after 120 h of cultivation, but activities at pH 7.0 as high as 317 U • g -1 could be obtained after 96 h. The activities measured at pH 9.0 were also promising, ranging from 177 to 191 U • g -1 . The results obtained are relevant, since high lipase activities, in a wide range of pH (4.0 to 9.0) were obtained from a newly isolated microorganism in a low-cost fermentation medium. The variation in the C/N ratio at the previously optimized conditions showed that the best results were obtained at C/N of 6.11.

The objective of this study was to evaluate yeast (Saccharomyces cerevisiae) from beer fermentation in its natural form (NY) and subjected to different processes of cellular ruptured [mechanical method using ultrasound (MRY) and modified autolysis using NaCl and ethanol (MAY)] regarding functional and digestibility properties, comparing them with textured soy protein (TSP). Ultrasound treatment resulted in 42% disruption efficiency and the micrographs obtained from scanning electron microscopy analysis showed important morphological modifications due to processes of cellular ruptured action. MRY cells presented more pronounced damage than LN, which suggests the rupture of the cell wall and exit of the internal material to the medium. NY, MRY, MAY, and TSP presented a very close composition concerning the protein content, ranging from 39.32 to 43.80% and moisture of 0.07-0.14%. In vitro digestibility of brewing yeast samples equated the digestibility of TSP (higher than 94%). Cellular disruption with ultrasound (MRY) caused an increase in foaming ability, stability and also oil retention capacity (8.82 mL of oil/g of protein). Modified autolysis (MAY) resulted in higher water holding capacity (14.50 g of water/ g of protein) and index of water solubility (greater than 64%) with a decrease in their emulsifying properties. The highest water absorption capacity was presented by the TSP and NY. Therefore, in its different forms, yeast can be applied as a functional and technological ingredient in the food industry, with significant technological capabilities and potential applications.

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