The hydrothermolysis variables temperature (150 -210 °C) and time (10 -20 minutes) were assessed to improve hydrolysis e ciency of brewery spent grain (BSG) for renewable energy generation. The intensi cation of the pretreatment was expressed by the severity variation (2.8 -4.5) and the process was optimized with methane production of 411.6 ± 7.2 mL. g -1 STV (severity 4.2). The fermentationmethanogenesis of BSG and hydrolysate resulting from BSG hydrothermolysis process under severity of 4.2 (210 o C for 10 min.) was evaluated by central composite design (CCD) with the variables operation temperature (30 -60 °C), BSG concentration (7.3 -20.7 g.L -1 ) and hydrolysate (0 -12.4 mL). The higher methane production observed was 305.8 mL.g -1 STV, with 14 g.L -1 of BSG, without hydrolysate at 45 °C.The main soluble metabolites were acetic acid (233.17 mg.L -1 ) and butyric acid (156.0 mg.L -1 ). On other hand, the lower methane production (108.5 ± 2.0 mL. g -1 STV) veri ed was 14 g.L -1 of BSG, 6.5 mL of hydrolysate at 60 °C, which revealed that in this condition propionic acid (947.4 mg.L -1 ) and acetic acid (599.2 mg.L -1 ) were expressive. In the optimal fermentation-methanogenic condition of pretreated BSG, Macellibacteroides and Sphaerochaeta (15.9 and 14.7%, respectively) were identi ed, as well as archaea similar to Methanosaeta (80.4%), favoring the acetoclastic methanogenic pathway.

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Brewers spent grain (BSG), the major by-product of brewing industry, can be used in anaerobic digestion for methane production, which can provide energy for brewery process. This study evaluated the methane production in batch reactors, in triplicates, at 37 ± 1°C, without agitation, from BSG under the following conditions: (1) raw, (2) pretreated in hydrothermal system (3) pretreated in autoclave. The inoculum source was obtained from upflow anaerobic slugde blanket reactor used in slaughterhouse of poultry. At first, an evaluation was accomplished using BSG (a) raw, (IN), pretreated, ground (T) milled (M), (b) raw and pretreated in hydrothermal system (INH), ground and pretreated in hydrothermal system (TH) and milled and pretreated in hydrothermal system. Hydrothermal pretreatment occurred at 180°C for 15 minutes under 9.6 bar. The highest methane production was observed in MH (320.64 ± 7.72 mL.g -1 STV) and higher volatile fatty acids was verified in M and MH, mainly butyric acid in M (388.32 mg.L -1 ) and acetic acid in MH (192.47 mg.L -1 ). A central composite design (CCD) involving two factors was held for evaluate the interaction between (x 1 ) hydrothermal pretreatment temperature and (x 2 ) hydrothermal pretreatment time for BSG. The range of temperature was 150-210 °C with runtime of 10 -20 minutes. Seven batch reactors assays was reached and the highest methane production (411.64 mL.g -1 STV) was verified for BSG pretreated at 210°C for 10 minutes under 12 bar. In this assay was observed carbohydrates consume of 90.45% (from 142 ± 1.41 mg.L -1 to 14.0 ± 1.41 mg.L -1 ) and COD removal of 81.12% (from 3.900 mg.L -1 to 627.5 ± 3.53 mg.L -1 ). BSG pretreated under this condition was employed in a CCD, with seventeen batch reactors condition, involving three variables (x 1 ) incubation temperature, (x 2 ) BSG concentration and (x 3 ) hydrolizate liquid from hydrothermal pretreatment. According to methodology of the CCD and response surface, the highest methane production was predicted in assay at 36°C, with 18 mg.L -1 and 3 mL of hydrolizate liquid. A CCD using BSG pretreated in autoclave was reached with two variables (x 1 ) incubation temperature and (x 2 ) BSG concentration. For this purpose, eleven batch reactors conditions were conducted, in triplicates, at temperature in the range of 30,86 -59,14°C and BSG concentration in the range of 8.34 a 19.66 mg.L -1 . By means of methodology of the CCD and response surface, the optimal predicted condition was at 35°C and 14 mg.L -1 with methane production of 289.10 mL.g -1 STV.

The hydrothermolysis variables temperature (150 - 210 °C) and time (10 - 20 minutes) were assessed to improve hydrolysis efficiency of brewery spent grain (BSG) for renewable energy generation. The intensification of the pretreatment was expressed by the severity variation (2.8 - 4.5) and the process was optimized with methane production of 411.6 ± 7.2 mL. g -1 STV (severity 4.2). The fermentation-methanogenesis of BSG and hydrolysate resulting from BSG hydrothermolysis process under severity of 4.2 (210 o C for 10 min.) was evaluated by central composite design (CCD) with the variables operation temperature (30 - 60 °C), BSG concentration (7.3 - 20.7 g.L -1 ) and hydrolysate (0 - 12.4 mL). The higher methane production observed was 305.8 mL.g -1 STV, with 14 g.L -1 of BSG, without hydrolysate at 45 °C. The main soluble metabolites were acetic acid (233.17 mg.L -1 ) and butyric acid (156.0 mg.L -1 ). On other hand, the lower methane production (108.5 ± 2.0 mL. g -1 STV) verified was 14 g.L -1 of BSG, 6.5 mL of hydrolysate at 60 °C, which revealed that in this condition propionic acid (947.4 mg.L -1 ) and acetic acid (599.2 mg.L -1 ) were expressive. In the optimal fermentation-methanogenic condition of pretreated BSG, Macellibacteroides and Sphaerochaeta (15.9 and 14.7%, respectively) were identified, as well as archaea similar to Methanosaeta (80.4%), favoring the acetoclastic methanogenic pathway.