The yeast autolysis process - an endogenous and irreversible lytic event, which occurs in cells caused by the action of intracellular enzymes, proteases and carbohydrases - is a well-known and an economic process, however, there is a constant risk of serious microbial contamination since there are many nutrients in the broth and this process is slow, favoring the growing of pathogens. The present work comes up with an attempt to accelerate the autolysis of Saccharomyces cerevisiae with focus on the high yield of yeast extract production through a fast, economic and simple technology. The proposed strategy is based on decreasing the pH of the yeast suspension at the beginning of autolysis through an acid shock to activate the cell autolytic system under stressful conditions of temperature and pH. The influence of cell concentration, temperature, time and acid shock at the beginning of the autolysis on yeast extract yields were studied. The best yields of proteins and total solids were observed for autolysis treated with acid shock (H2SO4 10 µL/g of dried yeast and final pH 4.4) at 60 °C (36, 84% of protein and 48, 47% of total solids extracted) and gradual increase of temperature 45 to 60 °C (41.20% of protein and 58.48% of total solids extracted). The shock could increase the speed of the process since the control reached about 30% of extract at 60 °C and the same experiment, however, with acid shock reached more than 43% in 12 h. When considering time in an industrial scale, it could be noted that the time was very important for the productivity as well as avoiding risk of pathogen contamination in autolysis. These results were very relevant for industrial purposes in the production of yeast extract, autolyzed yeast and glucan and mannan.

5'-ribonucleotides are high value-added molecules widely used in the food and pharmaceutical industries because of their bioactive properties. The present work aims to produce a composition of 5’-ribonucleotides using spent brewer’s yeast as cheap source of RNA, and barley malt rootlets as cheap source of 5'-phosphodiesterase (5'-PDE). This is a very promising and innovative strategy because both spent yeast and malt rootles are residues of the brewing process and are closely linked in a cycle that until now is not yet commercially exploited due to lack of studies. Our results showed that extraction of 5’-PDE was mainly influenced by the fineness of the rootlets and amount of extraction solvent (water). The main molecules formed during RNA hydrolysis were 5’-ribonucleotides, which represented 85.86% of the total hydrolyzed molecules. Finally, the results of the proposed approach can generate a new perspective for the brewing industry regarding the management of its wastes, generating from them products of high added value and with a wide range of applications.

The use of the I-Optimal mixture design technique of agro-industrial residues in cultivation submerged at 28°C for 15 days with Trichoderma reesei QM 9414, complemented with nutrients, was used to optimize the mixture for the production of fibrolytic enzymes. The results demonstrated that the use of 100% (m/v) of brewer's spent grain was promising for the production of total cellulases (0.42 FPU/mL) and xylanase (39.60 U/mL), as well as the use of 33.3% citrus pulp and 66.7% brewer's spent grain for the production of xylanase (40.2 U/mL). The combination of 16.67% wheat bran, 16.67% citrus pulp, and 66.7% brewer's spent grain was the most promising for the production of endoglucanase (2.03 U/mL), exoglucanase (3.20 U/mL), and β-glycosidase (0.12 U/mL). The study on the demand for minerals, sucrose, and yeast extract (as a vitamin and amino acid source) revealed that 0.1% yeast extract, 0.11% dibasic potassium phosphate, 0.0028% zinc, and 1% of sucrose in 12 days of culture were sufficient to maximize the production of cellulases, increasing by 2.38 times (1.0 FPU/mL) compared to the initial culture (0.42 FPU/mL). Cellulolytic production remained the same with the use of 0.01% tween 80 in citrus pulp (0.40 FPU/mL) compared to that obtained in the design with a brewer's spent grain without tween 80, however it reduced substantially (from 15 to 9 days) the cultivation time. On the other hand, the use of tween 80 dramatically inhibited the fungal production of xylanases (2.96 U/mL). The best combination of salts was combined with tween 80 to obtain 1.12 FPU / mL in 9 days of fermentation. An enzymatic hydrolysis of cassava bagasse was carried out by combining cellulases and amylases, reaching 48 g / L of reducing sugar. Thus, this work shows that by studying the influence of residues, kind of salts and concentration of tween 80, a more efficient and economical bioprocess was possible to obtain, as well as the association between fibrolytic enzymes.

The present work aims to produce a composition of 5'-ribonucleotides using spent brewer's yeast as cheap source of RNA and barley malt rootlets as cheap source of 5'-phosphodiesterase (5'-PDE). This strategy is very promising because both are residues of the brewing process and are closely linked in a cycle that until now is not yet commercially exploited due to lack of studies. The results of the present work showed that extraction of 5'-PDE was mainly influenced by the fineness of the rootlets and amount of extraction solvent (water). The main molecules formed during RNA hydrolysis were 5'-ribonucleotides, which represented 85.86% of the total hydrolyzed molecules. Finally, the results of the approach here proposed can generate a new perspective for the brewing industry in relation to the management of its wastes in order to generate from them products of high added value and with a wide range of applications.