Extraction and analysis of long chain fatty acids adsorbed onto active and inactivated anaerobic sludge

Extraction and GC analysis of the adsorbed long chain fatty acids onto active and inactivated sludge taken from two EGSB reactors fed with oleic acid as the sole carbon source at 6 kgCOD/m3.day was determined. No gradual acclimation of sludge to this LCFA was performed. Active sludge had been overloaded with oleic acid in a previous experiment and a possible retrieval of its activity was investigated. However the results revealed that the average removal efficiency was as low as 35% and only 19% of the biogas was methane. In the inactive reactor COD removal efficiency was 14%, corresponding only to physical adsorption, because no methane was produced. Extraction and analysis of the adsorbed fatty acids revealed that in the active sludge palmitic acid was the dominant fatty acid, in average, 3 to 52 times higher than oleic acid. In the inactivated sludge the main fatty acid detected was oleic acid, 8 times higher than palmitic acid

Sequencing adsorption and degradation cycles towards the methanization of long chain fatty acids : comparison between granular and suspended sludge

The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l (HRT=1 day). After removing the residual substrate, the sludge was incubated in batch vials without any added carbon source. A maximum methane production rate of 152±21 mlCH4(STP)/gVS.d was obtained for the RII-suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a cosubstrate (50% COD). The maximum plateau achieved in the methane production curve was 1145±307 mlCH4(STP)/gVS, obtained for the RII-suspended sludge taken on day 162, when oleate was fed as the sole carbon source at 6 g COD/l. Methanization rate of the adsorbed substrate was enhanced under stirring conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main adsorbed substrate was palmitate, and not oleate, as previously suspected. These results evidence the advantage of sequencing adsorption and degradation cycles for the treatment of effluents with high lipid content

Anaerobic degradation of oleic acid by suspended and granular sludge : identification of palmitic acid as a key intermediate

The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l (HRT = 1 day). After removing the residual substrate, the sludge was incubated in batch vials without any added carbon source. A maximum methane production rate of 152 ± 21 mlCH4(STP)/gVS.day was obtained for the suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a co-substrate (50% COD). The maximum plateau achieved in the methane production curve was 1145 ± 307 mlCH4(STP)/gVS, obtained for the suspended sludge taken on day 162, when oleate was fed as the sole carbon source at 6 g COD/l. The methanization rate of the adsorbed substrate was enhanced under stirring conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main adsorbed substrate was palmitate, and not oleate. Accumulated palmitate adsorbed onto the sludge and further β-oxidation was inhibited when in the presence of oleic acid. If oleic acid was removed from the medium β-oxidation proceeded with methane production. Suspended sludge was more efficient than granular sludge

GRASS UTILIZATION IN GROWING FINISHING BÍSARO PIGS (85-107 KG). PERFORMANCE AND CARCASS COMPOSITION

The use of different quantities of vegetables, forages or fresh grass as fodder for growing-finishing pigs is an important factor of the northern Portugal traditional system. The increasing development of swine production in outdoor systems, extensive and organic production, turns to upcoming natural diets, in which grass performs a significant part. With regard to this, some investigation has been made concerning the use of fibre-rich feed ingredients in pig nutrition. Metabolic effects of its ingestion are analysed concerning different sights (economical, social, environmental and physiological ones). The aim of this work was to study the effects of grass utilization in the diets on performances of finishing Bísaro pigs. A total of 22 pigs (16 castrated males and 6 females) was housed outdoor and fed ad libitum (37 – 85 kg live weight) with a growing diet and then transferred to an indoor system (with free access to an outdoor area) for 49 days, according to 3 different treatments: 100% concentrate (C), 75% concentrate + ad libitum grass (CE75), 50% concentrate + ad libitum grass (CE50). The grass was supplied and its intake registered on a daily basis. Every 14 days, the pigs were weighted and their back fat (P2 in vivo) measured. After slaughter (average weight of 107 kg LW), yield and ½ left carcass characteristics were controlled. During the outdoor growing phase, the ADG was 513 g/day. During the indoor finishing phase, the increase grass intake was proportional to the reduction of concentrate in the diet. The ADG (g) and the fat deposition (P2 cm) were significantly different (P<0,05) in the 3 treatments (ADG: C=641, CE75=467, CE50=356 and: C=11,4, CE75=+9,5, CE50=+6,2). The empty body weight (kg) was also proportional to the intake of concentrate (C=116,2; CE75=107,7; CE50=102,2). Comparatively to the weight of the body parts, pigs that had higher intake of grass and lower of concentrate showed a higher % of shoulder (P<0,05; C=20,4, CE75=21,7, CE50=22,2) and the pH45min of CE carcasses was significantly higher (P<0,05). As a conclusion, concentrate substitution for grass showed a slower growing rate, thinner carcasses and a high technological quality. Neverthelles variability (CV %) of the productive parameters at the end of this study were higher in the treatments that included grass: live weight (C= 10,5%; C75=10,7%; C50=14,3%), finishing ADG (C=24%; C75=37%, C50=42%), and final fat (C=37%; C75=32%, C50=52%). These values suggest that the utilization of fibrous feeds in growing-finishing swine may be one of the possible explanations of the more heterogeneous products and carcasses found in the traditional or extensive systems, common users of fibrous feeds in the carcass finishing phase