RESUMO
Abstract Considering the importance of lignocellulose macrophyte-derived for the energy flux in aquatic ecosystems and the nutrient concentrations as a function of force which influences the decomposition process, this study aims to relate the enzymatic activity and lignocellulose hydrolysis in different trophic statuses. Water samples and two macrophyte species were collected from the littoral zone of a subtropical Brazilian Reservoir. A lignocellulosic matrix was obtained using aqueous extraction of dried plant material (≈40 °C). Incubations for decomposition of the lignocellulosic matrix were prepared using lignocelluloses, inoculums and filtered water simulating different trophic statuses with the same N:P ratio. The particulate organic carbon and dissolved organic carbon (POC and DOC, respectively) were quantified, the cellulase enzymatic activity was measured by releasing reducing sugars and immobilized carbon was analyzed by filtration. During the cellulose degradation indicated by the cellulase activity, the dissolved organic carbon daily rate and enzyme activity increased. It was related to a fast hydrolysable fraction of cellulose that contributed to short-term carbon immobilization (ca. 10 days). After approximately 20 days, the dissolved organic carbon and enzyme activity were inversely correlated suggesting that the respiration of microorganisms was responsible for carbon mineralization. Cellulose was an important resource in low nutrient conditions (oligotrophic). However, the detritus quality played a major role in the lignocelluloses degradation (i.e., enzyme activity) and carbon release.
Assuntos
Bactérias/enzimologia , Proteínas de Bactérias/metabolismo , Celulase/metabolismo , Araceae/metabolismo , Paspalum/metabolismo , Água Doce/química , Lignina/metabolismo , Brasil , Carbono/metabolismo , Celulose/genética , Celulose/metabolismo , Ecossistema , Araceae/crescimento & desenvolvimento , Araceae/microbiologia , Paspalum/crescimento & desenvolvimento , Paspalum/microbiologia , Água Doce/microbiologiaRESUMO
Enzymatic activity during decomposition is extremely important to hydrolyze molecules that are assimilated by microorganisms. During aquatic macrophytes decomposition, enzymes act mainly in the breakdown of lignocellulolytic matrix fibers (i.e. cellulose, hemicellulose and lignin) that encompass the refractory fraction from organic matter. Considering the importance of enzymatic activities role in decomposition processes, this study aimed to describe the temporal changes of xylanase and cellulose activities during anaerobic decomposition of Ricciocarpus natans (freely-floating), Oxycaryum cubense (emergent) and Cabomba furcata (submersed). The aquatic macrophytes were collected in Óleo Lagoon, Luiz Antonio, São Paulo, Brazil and bioassays were accomplished. Decomposition chambers from each species (n = 10) were set up with dried macrophyte fragments and filtered Óleo Lagoon water. The chambers were incubated at 22.5ºC, in the dark and under anaerobic conditions. Enzymatic activities and remaining organic matter were measured periodically during 90 days. The temporal variation of enzymes showed that C. furcata presented the highest decay and the highest maximum enzyme production. Xylanase production was higher than cellulase production for the decomposition of the three aquatic macrophytes species.
RESUMO
Decomposition of lignocellulosic detritus at enzymatic level is the rate-limiting step during aquatic macrophyte decomposition. Assays were carried out to evaluate cellulase activity during decomposition of Utricularia breviscapa; the assays included the following C-sources: leachate, lignocellulosic matrix and integral detritus. The incubations comprised U. breviscapa C-sources added to Óleo lagoon (21º 36'S and 47º 49'W) water maintained in the dark under anaerobic condition at 15ºC, 20ºC, 25ºC and 30ºC. Cellulase activity were monitored during 180 days, with the activity showing a time evolution that depended on the temperature and type of detritus: (i) cellulase activity tended to occur earlier with increasing temperatures, but it was less intense than at lower temperatures, (ii) no activity was observed in incubations with leachate, (iii) cellulase activity was observed in the incubation with integral detritus and lignocellulosic matrix and (iv) higher cellulase activity was observed in the incubations with integral detritus at 15ºC (P 0.05).
A decomposição dos detritos lignocelulósicos em nível enzimático é uma etapa limitante da decomposição de macrófitas aquáticas. Experimentos foram realizados para avaliar a atividade da celulase durante a decomposição de diferentes fontes de carbono provenientes de Utricularia breviscapa: lixiviado, matriz lignocelulósica e detritos íntegros. As incubações compreenderam as fontes de carbono de U. breviscapa adicionadas à água da lagoa do Óleo (21º 36'S e 47º 49'W) mantida no escuro à 15ºC, 20ºC, 25ºC e 30ºC. As atividades da celulase foram monitoradas durante 180 dias, apresentando uma evolução temporal dependente da temperatura e do tipo de detrito: (i) a atividade da celulase tendeu a ocorrer mais cedo nas temperaturas mais elevadas, porém foram menos intensas, que nas temperaturas mais baixas, (ii) nenhuma atividade foi observada nas incubações com lixiviado, (iii) as atividades da celulase foram observadas nas incubações com detritos integrais e com matriz lignocelulósica e (iv) as atividades da celulase foram mais elevadas nas incubações com detritos integrais à 15ºC (P 0,05).
RESUMO
This study describes the aerobic and anaerobic decay of soluble carbohydrates (CH) and polyphenols (PH) during decomposition of Montrichardia arborescens. Plant and water samples were collected in the Cantá stream (2º 49' 11" N and 60º 40' 24" W), Roraima, Brazil. Decomposition chambers with plant fragments and stream water were incubated. Particulate organic matter was separated from dissolved organic matter and concentrations of CH and PH were determined. The results were fitted to 1st order kinetics models. CH and PH comprised a labile fraction (LCH and LPH) and a refractory fraction (RCH and RPH). The global coefficient associated with LCH weight loss was 1.4 times higher under aerobic conditions (3.4 day-1) higher than for anaerobic conditions. On the other hand, the RCH decay rate in the anaerobic process (0.0074 day-1) was 1.39 times higher. LCH was estimated to be 92% while RCH amounted to 8%. The LPH anaerobic decay was 5.2 times the value for the aerobic decay (0.67 day-1). For both conditions, RPH decay coefficients were similar (¼ 0.011 day-1). In the aerobic experiments LPH and RPH corresponded to 92.5% and 7.5%, respectively. For the anaerobic process these contents were 85.5% and 14.5%, respectively. From these results, we concluded that in the Cantá stream, the anaerobic degradation of phenols is more efficient than the aerobic counterpart. The aerobic condition provides a faster decay of carbohydrates of this plant.
Este estudo descreveu o decaimento aeróbio e anaeróbio de carboidratos (CH) e polifenóis (PH) durante a decomposição de Montrichardia arborescens. As amostras de planta e de água foram coletadas no igarapé do Cantá (2º 49 ' 11 " N e 60º 40 ' 24 " W), Roraima, Brasil. Câmaras de decomposição contendo fragmentos de plantas e água do iguarapé foram incubadas. A matéria orgânica particulada foi separada da dissolvida e as concentrações CH e PH foram determinadas. Os resultados foram ajustados a um modelo cinético de 1ª ordem. O CH e o PH apresentaram duas frações: uma lábil (LCH e LPH) e uma refratária (RCH e RPH). Verificou-se que o coeficiente global relacionado com a perda de massa do LCH para condição aeróbia (3,4 dia-1) foi 1,4 vezes mais elevado que para a anaeróbia. Por outro lado, o coeficiente de decaimento do RCH para o processo anaeróbio (0,0074 dia-1) foi 1,39 vezes mais elevado. O LCH foi estimado em 92% e o refratário em 8%. A degradação anaeróbia de LPH foi 5,2 vezes mais elevada que a aeróbia (0,67 dia-1). Os coeficientes de decaimento do RPH foram similares (¼ 0,011 dia-1) para ambas condições. Para o experimento aeróbio, o LPH e o RPH corresponderam a 92,5% e 7,5%. Para os processos anaeróbios estas frações foram de 85,5% e 14,5%, respectivamente. A partir destes resultados, supõe-se que no igarapé do Cantá, a degradação anaeróbia dos polifenóis seja mais eficiente que a aeróbia. A condição aeróbia promove um decaimento mais rápido dos carboidratos desta planta.