Geraldo L. Sant'Anna

Lipase production by solid-state fermentation: cultivation conditions and operation of tray and packed-bed bioreactors.

The production of lipase by Penicillium simplicissimum in solid-state fermentation was studied using babassu cake as the basal medium. Tray-type and packed-bed bioreactors were employed. In the former, the influence of temperature; content of the medium, and medium supplementation with olive oil, sugarcane molasses, corn steep liquor, and yeast hydrolysate was studied. For all combinations of supplements, a temperature of 30°C, a moisture content of 70%, and a concentration of carbon source of 6.25% (m/m, dry basis) provided optimum conditions for lipase production. When used as single supplements olive oil and molasses also were able to provide high lipase activities (20 U/g). Using packed-bed bioreactors and molasses-supplemented medium, optimum conditions for enzyme production were air superficial velocities above 55 cm/min and temperatures below 28°C. The lower temperature optimum found for these reactors is probably related to radial heat gradient formation inside the packed bed. Maximum lipase activities obtained in these bioreactors (26.4 U/g) were 30% higher than in tray-type reactors.

HYDROLYTIC ENZYMES AS COADJUVANTS IN THE ANAEROBIC TREATMENT OF DAIRY WASTEWATERS

An enzymatic extract produced by Penicillium restrictum having a high level of lipase activity (17.2 U.g-1) was obtained by solid-state fermentation using babassu cake as substrate. The enzymatic extract was used in the hydrolysis of a dairy wastewater with high fat contents (180, 450, 900 and 1,200 mg.L-1). Different hydrolysis conditions were tested, and it was determined that it should be carried out at a temperature of 35oC, without agitation, with 10% v/v enzymatic extract and a hydrolysis time of 12 hours. Both crude and hydrolysed effluents were then submitted to an anaerobic biological treatment. It was observed that for the enzymatically pretreated effluent there was a significant improvement in the efficiency of the anaerobic treatment. For the highest fat content tested (1,200 mg.L-1), removal efficiencies of 19 and 80% were attained for crude and hydrolysed effluents, respectively. In addition, a tenfold increase in the removal rate of COD from the hydrolysed effluent (1.87 kg COD.m-3.d-1) was observed in relation to the crude effluent (0.18 kg COD.m-3.d-1). The results obtained in this study illustrate the viability of using a hybrid treatment (enzymatic-biological) for wastewaters having high fat contents.

Remediation of sandy soils using surfactant solutions and foams.

Remediation of sandy soils contaminated with diesel oil was investigated in bench-scale experiments. Surfactant solution, regular foams and colloidal gas aphrons were used as remediation fluids. An experimental design technique was used to investigate the effect of relevant process variables on remediation efficiency. Soils prepared with different average particle sizes (0.04-0.12 cm) and contaminated with different diesel oil contents (40-80 g/kg) were used in experiments conducted with remediation fluids. A mathematical model was proposed allowing for the determination of oil removal rate-constant (k(v)) and oil content remaining in the soil after remediation (C(of)) as well as estimation of the percentage of oil removed. Oil removal efficiencies obtained under the central experimental design conditions were 96%, 88% and 35% for aphrons, regular foams and surfactant solutions, respectively. High removal efficiencies were obtained using regular foams and aphrons, demanding small amounts of surfactant.

Phenol removal through combined biological and enzymatic treatments

This work studies the use of biological and combined biological/enzymatic treatments in phenol degradation. The systems studied were conventional batch aerobic biological followed or preceded by enzymatic treatment. Tyrosinase extracted from the mushroom Agaricus bispora was employed. Biological treatment efficiently degraded effluents containing up to 420 mg.L-1 of phenol, removing 97% of the COD and 99% of the phenol in 48-hour batches. Alterations in phenol concentration intake reduced treatment efficiency significantly. Enzymatic polishing of biotreated effluent removed up to 75% of the remaining phenol in a four-hour reaction with 46 U.mL-1 of tyrosinase and 50 mg.L-1 of chitosan (used as coagulant). Enzymatic pretreatment with 20 U.mL-1 of tyrosinase reduced the phenol concentration by 25 % after 2 hours of reaction, although initial COD increased up to 58%. The subsequent biological treatment of that enzymatic pretreated effluent reduced COD to 151 mgO2.L-1 and phenol concentration to 1 mg.L-1 in 24-hours batches.

Photocatalysis as a tertiary treatment for petroleum refinery wastewaters

Photocatalysis has been used as tertiary treatment for petroleum refinery wastewaters to comply with the regulatory discharge limits and to oxidize persistent compounds that had not been oxidized in the biological treatment. The wastewater is generated by the refinery and directly discharged into the Guanabara Bay (Rio de Janeiro). Although BOD removal is high, a residual and persistent COD, besides a somewhat high phenol content remains. Three photocatalysts were tested - TiO2 (Aldrich), ZnO (Aldrich), and TiO2 (P25, Degussa) - the third being the most active. The optimized conditions obtained with an experimental design were 3.0 g L-1 TiO2 and pH 6.3. The use of hydrogen peroxide (H2O2) showed no beneficial effect. Removal of 93% of phenols, 63% of dissolved organic carbon (DOC), and more than 50% of oil and grease (OG) were achieved in the photocatalytic process, improving the quality of the treated wastewater.

Penicillium restrictum lipases: A comparative study and characterization of enzymes with different degrees of purity

Penicillium restrictum was identified as a promising strain for lipase production due to enzyme production yield and thermal stability of the enzyme. This work presents results of lipase purification and enzyme stability versus pH. Ultrafiltration and precipitation with ammonium sulphate were used as initial purification steps. The partially purified enzyme preparation showed an increase in stability as pH increased. The crude enzymatic preparation was assayed with different oils and tributirin and showed a major catalytic activity for triglycerides of medium/long-chain fatty acids. Further purification steps were conducted on an analytical scale. The initial attempt to use gel filtration was abandoned as lipase lost its stability after this chromatographic procedure. The fast ion-exchange chromatography was performed on a Mono Q column, and two peaks with lipolytic activity were isolated and analysed by electrophoresis.

Molecular weight distribution of chlorolignin in bleached Kraft effluent by GPC and ultrafiltration

Abstract The molecular weight distribution (MWD) of chlorinated compounds of bleached Kraft pulp mill effluent was investigated by aqueous gel permeation chromatography (GPC) and ultrafiltration. The effluent was fractionated by ultrafiltration, using different cut-off membranes (MW 50 000, 20 000, 10 000 and 8000). The retentate and permeate of each ultrafiltration was analyzed by GPC. The results showed that the molecular weight distribution for all samples ranged from 200 to 550 Da. Two effects were discussed: associative interactions between the compounds to form high molecular associated complexes (aggregates); and non-size-exclusion effects, like ion exclusion. Aggregates formation was confirmed by ultrafiltration experiments, using a 50 000 cut-off membrane.

Ethanol from babassu coconut starch: technical and economical aspects.

This study describes a pioneering industrial-scale experience by Tobasa in ethanol production from the amylaceous flour obtained by mechanical processing of the babassu mesocarp. Technical aspects related to enzymatic and fermentation processes, as well as overall economical aspects, are discussed. When produced in a small-size industrial plant (5000 L/d), babassu ethanol has a final cost of about

The bioactivation procedure for increasing the sulphate-reducing bacteria in a UASB reactor

218/m3. The impact of raw materials, production, and processing (enzymes, steam, energy, and so on) on the final product cost is also presented. Babassu coconut ethanol can be produced at low cost, compared with traditional starchy raw materials or sugar cane. The net profitability of ethanol production is about 40% for babassu coconut and just 10% for sugar cane. If the estimated renewable babassu resources were entirely industrially used, 1 billion L/yr of ethanol could be produced, which would roughly correspond to 8% of the current Brazilian ethanol production.

Mathematical Modeling of Lipase and Protease Production by Penicillium restrictum in a Batch Fermenter

Bioactivation, a procedure to obtain anaerobic sulphidogenic sludge, was developed in order to increase sulphate reduction and, consequently, sulphide production to remove metals from effluents. This procedure, in which the source of carbon/energy (lactate) is gradually replaced, consisted of three operational conditions. It was observed that bioactivation took six months so there was a 100-fold increase in the population of sulphate-reducing bacteria estimated by the most-probable-number (MPN) when molasses was employed as a new source.