The enzymatic hydrolysis of steam-pretreated sugarcane bagasse, either delignified or non-delignified, was studied as a function of enzyme loading. Hydrolysis experiments were carried out using five enzyme loadings (2.5 to 20 FPU/g cellulose) and the concentration of solids was 2% for both materials. Alkaline delignification improved cellulose hydrolysis by increasing surface area. For both materials, glucose concentrations increased with enzyme loading. On the other hand, enzyme loadings higher than 15 FPU/g did not result in any increase in the initial rate, since the excess of enzyme adsorbed onto the substrate restricted the diffusion process through the structure.

Paclobutrazol is growth regulator of plants that has low mobility in soil and therefore has accumulated. The objective of this study was to investigate the paclobutrazol biodegradation in two soils from the São Francisco River Valley. The biodegradation experiments were conducted in batch using paclobutrazol and paclobutrazol added glycerol. The experiments were performed in sterile and nonsterile conditions using a mixed culture of Pseudomonas. The concentration of paclobutrazol was determined by high performance liquid chromatography. The biodegradation reached 43% in 14 days of experiments with only paclobutrazol and 70% in 28 days of experiments that contained glycerol and paclobutrazol.

Mathematical models can help to prevent high levels of toxic substances in soil or fruits of plants treated with pesticides and indicate that such substances should be systematically monitored. The aim of this research was to study the kinetics of paclobutrazol biodegradation by soil native bacteria using mathematical models. Three models were used to assess the kinetics of paclobutrazol biodegradation obtained experimentally. Excellent fits were obtained using dual kinetic and logistic models. The use of glycerol as additional carbon source increased the biodegradation of PBZ and consequently decreased the time required for a given PBZ initial concentration be halved.

A fisiologia de B. subtilis R14 foi investigada em meio mínimo em condições de excesso e limitação de oxigênio. Crescimento e esporulação eficientes foram obtidas em culturas com excesso de oxigênio em meio contendo fontes de carbono e nitrogênio de fácil assimilação, que permitiram alta taxa de crescimento e alto rendimento em biomassa. Uma fase de transição curta, entre o crescimento exponencial e a esporulação, pode ser obtida pela formulação de um meio com razão C/N balanceada. Sob limitação de oxigênio, mas em presença de nutrientes essenciais, B. subtilis R14 produziu compostos bioativos. Os compostos apresentaram atividade contra várias bactérias fitopatogênicas. Sob condição de anaerobiose, o microrganismo não cresceu, nem através de fermentação nem de respiração anaeróbica. A adição de piruvato ao meio permitiu o crescimento, tanto através de fermentação como de respiração anaeróbica. O conhecimento adquirido neste trabalho é relevante tanto para o projeto do processo de produção quanto para a formulação de um produto comercial eficiente para biocontrole.

The physiology of B. subtilis R14 was investigated in minimal medium under excess-oxygen and oxygen-limited conditions. Growth and efficient sporulation could be achieved in excess-oxygen culture on medium with readily metabolizable carbon and nitrogen sources, which allowed high growth rate and high biomass yield. A short transition phase between the exponential growth and sporulation could be attained by formulating a medium with a well-balanced C/N ratio. Under oxygen-limitation, but in the presence of essential nutrients (i.e. excess-nutrient cultivation), B. subtilis R14 produced bioactive compounds, which showed activity against several phytopathogenic bacteria. Under anaerobic condition, the organism did not grow neither through fermentation nor anaerobic respiration. However, addition of pyruvate to the medium allowed its growth through fermentation and anaerobic respiration. The knowledge acquired in this work could be relevant both for the design of a production process as well as for the formulation of an effective commercial biocontrol product.

In this work, four different process configurations, including three simultaneous saccharification and fermentation (SSF) schemes and one separate hydrolysis and fermentation (SHF) scheme, were compared, at 8% water-insoluble solids, regarding ethanol production from steam-pretreated and alkali-delignified sugar cane bagasse. Two configurations included a 16 h lasting enzymatic presaccharification prior to SSF, and the third one was a classical SSF without presaccharification. Cellulose conversion was higher for the delignified bagasse, and higher in SSF experiments than in SHF. The highest cellulose-to-ethanol conversion (around 60% in 24 h) and maximum ethanol volumetric productivities (0.29-0.30 g/L.h) were achieved in the presaccharification-assisted SSF.

In this work, a methodology for the characterization of sugar cane bagasse was validated. Bagasse pre-treated with steam in a 5000 L reactor at a pressure of 15.3 kgf/cm², during 7 min, was used to test the methodology. The methodology consisted of the hydrolysis of the material with H2SO4 at 72% v/v, for the quantification of carbohydrates, organic acid, furfural and hydroxymethylfurfural by HPLC; insoluble lignin and ash by gravimetry; and soluble lignin by spectrophotometry. Linearity, repeatability, reproducibility and accuracy of the results obtained in two Research Laboratories were determined, and were considered to be suitable for the validation of the methodology.

O paclobutrazol (PBZ) é um regulador de crescimento utilizado em sistemas agrícolas com o propósito de controlar o crescimento vegetativo, estimulando a capacidade reprodutiva das plantas. Esse regulador de crescimento permanece ativo no solo por muito tempo, e sua meia-vida varia com o tipo de solo e as condições climáticas, podendo afetar severamente o desenvolvimento dos cultivos subseqüentes e, por lixiviação, contaminar os aqüíferos. Este trabalho teve como objetivo estudar os mecanismos envolvidos no transporte e na sorção do PBZ em colunas, utilizando amostras de um Argissolo Amarelo eutrófico e de um Vertissolo Háplico órtico, ambos da região do Vale do Rio São Francisco. Os ensaios de deslocamento miscível do traçador (solução de KBr) e do paclobutrazol foram realizados considerando duas vazões (0,4 e 1,6 cm³ min-1) para ambos os solos. As variáveis hidrodispersivas foram obtidas pelo ajuste do modelo convecção dispersão (CDE) às curvas de eluição experimentais do KBr, e as variáveis do modelo CDE-2 sítios de sorção, às curvas de eluição experimentais do PBZ por intermédio do programa CXTFIT 2.0. O paclobutrazol foi mais facilmente transportado no Vertissolo Háplico que no Argissolo Amarelo. A taxa de recuperação foi menor para a menor vazão para ambos os solos. A quantidade de PBZ não recuperada pode ser atribuída, sobretudo, à histerese no processo de sorção irreversível. O modelo CDE a dois sítios de sorção representa adequadamente os dados experimentais das curvas de eluição do paclobutrazol. Os resultados obtidos evidenciam que o paclobutrazol, utilizado em pomares com manga irrigada cujos solos são o Argissolo Amarelo e o Vertissolo Háplico, oferece risco real de contaminação das águas subterrâneas da região.

Paclobutrazol (PBZ) is a post-emergence plant growth regulator used in agricultural systems with the objective of vegetative control growth, thereby increasing the reproductive capacity of the plant. This growth regulator remains active in the soil for several years being detrimental to subsequent tillage and contamination of groundwater through leaching. The objective of this work was to study the mechanisms involved in the transport and sorption of PBZ in an Ultisol and a Vertisol, both of the São Francisco Valley, Brazil. Column breakthrough experiments were performed with a water tracer (Bromide) and with PBZ at 0.4 e 1.6 cm³.min-1 in the two soils. Hydrodispersive parameters of both soils were obtained by fitting the tracer breakthrough curves (BTC) with the convection-dispersion (CDE) model, whereas the parameters of PBZ reactive transport were obtained with the CDE-2 sorption sites model, through the CXTFIT code. PBZ presents a lower retardation factor in the Vertisol than in the Ultisol. The water flow was found to strongly affect PBZ mass balance, mainly because of sorption/desorption hysteresis, suggesting partial irreversible sorption of the chemical. The two sites model fitted well the tracer and PBZ breakthrough curves. The results showed that PBZ transport is strongly influenced by its interactions with the soil matrix through rate-limited sorption. The determined transport parameters indicate that PBZ applied to the two tropical soils cultivated with Mango presents an important leaching potential and contamination risk of the groundwater of the São Francisco Valley.

Paclobutrazol is a plant growth retardant which is used world-wide for increasing the yield of cereal crops. However, this compound remains active in the soil for several years and can severely affect the growth and development of subsequent crops, mainly by reducing vegetative vigor. The aim of this work was to develop and validate methods for the determination of paclobutrazol concentrations by both high performance liquid chromatography and spectroscopy. Both methods were satisfactory and showed appropriately low quantification limits. The determination by spectroscopy has, however, the advantage of being a method significantly less expensive than high performance liquid chromatography.

A mancha-aquosa, causada por Acidovorax avenae subsp. citrulli (Aac) causa grandes prejuízos à cultura do melão. O controle dessa doença foi estudado in vivo, com microbiolização de sementes de melão Amarelo infectadas, com líquidos fermentados de Bacillus subtilis R14, B. megaterium pv. cerealis RAB7, B. pumilus C116 e Bacillus sp. MEN2, com e sem células bacterianas. O mecanismo de ação dos isolados foi estudado in vitro pelo método de difusão em ágar e os compostos bioativos parcialmente caracterizados por testes de hemólise e atividade surfactante. Nos testes in vivo, não houve diferença significativa entre os tratamentos com e sem células, indicando que o controle ocorreu devido à presença de compostos bioativos produzidos durante as fermentações. Todos os tratamentos diferiram da testemunha sem diferir entre si (P=0,05%). B. megaterium pv. cerealis RAB7 proporcionou redução da incidência (89,1%) e do índice de doença (92,7%), elevou o período de incubação da mancha-aquosa de 9,8 para 11,9 dias e reduziu a AACPD de 3,36 para 0,17. In vitro, todos isolados apresentaram antibiose contra Aac e os compostos bioativos foram parcialmente caracterizados como lipopeptídeos.

The bacterial fruit blotch, caused by the bacterium Acidovorax avenae subsp. citrulli (Aac), is responsible for great losses in melon production. The control of this disease was investigated in vivo by treating infected yellow melon seeds with fermented broths of B. subtilis R14, B. megaterium pv. cerealis RAB7, B. pumilus C116 and Bacillus sp. MEN2, with and without bacterial cells. The mechanism of action of the strains was studied in vitro by the agar diffusion technique. The bioactive compounds produced were partially characterized by hemolysis test and surfactant activity. Regarding the tests conducted in vivo there was no statistical difference between the treatments with and without bacterial cells, which indicated that the control was due to the presence of bioactive compounds produced during fermentations. All treatments were different from the control (P = 0.05%) but they did not differ among them. The B. megaterium pv. cerealis RAB7 reduced disease incidence (89.1%), disease index (92.7%), increased the incubation period from 9.8 to 11.9 days and reduced the area under disease progress curve from 3.36 to 0.17. In the in vitro tests, all strains showed antibiosis against Aac and the bioactive compounds were partially characterized as lipopeptides.