Luciane Sene

Toluene and styrene removal from air in biofilters

Abstract Two identical sized laboratory-scale biofilters, filled with the same type of packing material, consisting of a mixture of peat and glass beads in a 4:1 volume ratio, are investigated for the purification of toluene and styrene-containing off-gas streams. One of the biofilters was inoculated with a toluene-degrading strain of Acinetobacter sp. NCIMB 9689, and the other with a styrene-degrading strain of Rhodococcus rhodochrous AL NCIMB 13259. For both pollutants, different sets of continuous experiments were conducted in the biofilter columns, varying both the inlet pollutant concentration and the superficial gas velocity. Maximum elimination capacities of 242 and 63 g m packing material −3 h −1 packing material were recorded for toluene and styrene, respectively. Furthermore, the deodorization (defined as the achievement of a pollutant concentration in the effluent gas below the pollutant olfactory threshold value) of toluene and styrene-containing waste-gases was also considered. This was achieved, operating at maximum inlet concentrations of 1.99 and 0.20 g m −3 and at superficial gas velocities of 17.8 and 122 m h −1 , respectively.

Sugarcane bagasse as alternative packing material for biofiltration of benzene polluted gaseous streams: a preliminary study

Removal of benzene vapor from gaseous streams was studied in two identically sized lab-scale biofiltration columns: one filled with a mixture of raw sugarcane bagasse and glass beads, and the other one packed with a mixture of ground sugarcane bagasse and glass beads, in the same volume ratio, as filter materials. Separate series of continuous tests were performed, in parallel, under the same operating conditions (inlet benzene concentration of 10.0, 20.0 or 50.0 mg m(-3), and superficial gas velocity of 30.6, 61.2 or 122.4 m h(-1)) in order to evaluate and compare the influence of the packing material characteristics upon the biofilter effectiveness. The maximum elimination capacities obtained, at an inlet load of 6.12 g m(-3) h(-1), were 3.50 and 3.80 g m(-3)packibng material h(-1) with raw and ground sugarcane bagasse, respectively. This was a preliminary study and the results obtained suggest only a limited application with more work needed.

New aspects on atrazine biodegradation

The world practice of using agrochemicals for long periods, in an indiscriminated and abusive way, has been a concern of the authorities involved in public health and sustainability of the natural resources, as a consequence of environmental contamination. Agrochemicals refer to a broad range of insecticides, fungicides and herbicides, and among them stands out atrazine, a herbicide intensively used in sugarcane, corn and sorghum cultures, among others. Researches have demonstrated that atrazine has toxic effects in algae, aquatic plants, aquatic insects, fishes and mammals. Due to the toxicity and persistence of atrazine in the environment, the search of microbial strains capable of degrading it is fundamental to the development of bioremediation processes, as corrective tools to solve the current problems of the irrational use of agrochemicals. This review relates the main microbial aspects and research on atrazine degradation by isolated microbial species and microbial consortia, as well as approaches on the development of techniques for microbial removal of atrazine in natural environments.

Enhanced Xylitol Production by Precultivation of Candida guilliermondii Cells in Sugarcane Bagasse Hemicellulosic Hydrolysate

The present work evaluated the key enzymes involved in xylitol production (xylose reductase [XR] and xylitol dehydrogenase [XDH]) and their correlation with xylose, arabinose, and acetic acid assimilation during cultivation of Candida guilliermondii FTI 20037 cells in sugarcane bagasse hemicellulosic hydrolysate. For this purpose, inocula previously grown either in sugarcane bagasse hemicellulosic hydrolysate (SBHH) or in semidefined medium (xylose as a substrate) were used. The highest xylose/acetic acid consumption ratio (1.78) and the lowest arabinose consumption (13%) were attained in the fermentation using inoculum previously grown in semidefined medium (without acetic acid and arabinose). In this case, the highest values of XR (1.37 U mg prot−1) and XDH (0.91 U mg prot−1) activities were observed. The highest xylitol yield (∼0.55 g g−1) and byproducts (ethanol and glycerol) formation were not influenced by inoculum procedure. However, the cell previously grown in the hydrolysate was effective in enhancing xylitol production by keeping the XR enzyme activity at high levels (around 0.99 U·mgprot−1), reducing the XDH activity (34.0%) and increasing xylitol volumetric productivity (26.5%) with respect to the inoculum cultivated in semidefined medium. Therefore, inoculum adaptation to SBHH was shown to be an important strategy to improve xylitol productivity.

Metabolic study of the adaptation of the yeast Candida guilliermondii to sugarcane bagasse hydrolysate

Abstract. Batch xylitol production from concentrated sugarcane bagasse hydrolysate by Candida guilliermondii was performed by progressively adapting the cells to the medium. Samples were analyzed to monitor sugar and acetic acid consumption, xylitol, arabitol, ethanol, and carbon dioxide production, as well as cell growth. Both xylitol yield and volumetric productivity remarkably increased with the number of adaptations, demonstrating that the more adapted the cells, the better the capacity of the yeast to reduce xylose to xylitol in hemicellulose hydrolysates. Substrate and product concentrations were used in carbon material balances to study in which way the different carbon sources were utilized by this yeast under microaerobic conditions, as well as to shed light on the effect of the progressive adaptation to the medium on its fermentative activity. Such a theoretical means allowed estimation for the first time of the relative contribution of each medium component to the formation of the main products of this fermentation system.

Adaptation and reutilization of Candida guilliermondii cells for xylitol production in bagasse hydrolysate

The xylitol productivity increased by about 15% with the use of cells of Candida guilliermondii FTI 20037 previously recycled through four consecutive batch cultures and adapted to the sugar cane bagasse hemicellulosic hydrolysate. Furthermore, the more concentrated the hydrolysate, the more necessary was the adaptation of the cells, owing to the presence of toxic substances at high concentration which inhibited the xylose‐xylitol conversion by the yeast.

Batch kinetics of Pseudomonas sp. growth on benzene. Modeling of product and substrate inhibitions.

Batch tests of benzene degradation were performed in liquid phase at 30 °C, pH 6.8 ± 0.2, and 200 rpm in two 3‐L stirred tank bioreactors, using the benzene‐degrading bacterium Pseudomonas sp. NCIMB 9688. A relatively high starting biomass level (220–270 mgX/L) and starting benzene concentration ranging from 20 to 200 mgS/L were selected as conditions to investigate possible inhibition phenomena. Volumetric as well as specific rates of biomass formation and substrate consumption were calculated from experimental data of both growth and benzene degradation and used to propose and check a new overall kinetic model for cell growth simultaneously accounting for both product and substrate inhibitions. The results of the present study evidenced the occurrence of a competitive‐type product inhibition due to 2‐hydroxymuconic semialdehyde ( KiP′ = 0.902 mgS/L), which was stronger than the uncompetitive‐type inhibition exerted by substrate ( KiS = 7.69 mgS/L).

Vanillin production by recombinant strains of Escherichia coli

Vanillin production from ferulate was studied using different recombinant strains of Escherichia coli. To prevent the occurrence of aerobic conditions and then possible product oxidation, tests were performed in Erlenmeyer flasks under mild mixing (150 rpm). Among other transformants, E. coli JM109(pBB1) appeared to be the best vanillin producer, being able to convert no less than 95% of starting ferulate to the product within 1h. This yield decreased down to 72% after 72h, likely because of a non-specific oxidase activity responsible for vanillin oxidation to vanillate.

Selection of microorganisms producer of lipase for fat removal from biodiesel purification water

The objective this study has been the selection of lipase productor microorganism, for removal of oils and grease, in the pre-treatment of biodiesel wastewater washing. For this, analyses of the physicist-chemistries characteristics had been made with the wastewater of the biodiesel washing, and then it had been isolated and chosen, by means of determinations of the lipase activity. Following, it was made a test of fat biodegradation, in the conditions: pH (5.95), temperature (35 oC), rotation (180 rpm) and ammonium sulfate as nitrogen source (3 g L-1) and establishing as variable the two microorganism preselected and the time (24; 48; 72; 96 and 120 h). The biodiesel purification wastewater had presented high potential of environmental impact, presenting a concentration of O of 6.76 g L-1. From the six isolated microbiological cultures, two microorganisms (A and B) had been selected, with enzymatic index of 0.56 and 0.57, respectively. The treatment of the wastewater using the isolated microorganism (Klebsiella oxytoca) had 80% of the fatty removal in 48 h.

Isolation of filamentous fungi present in swine wastewater that are resistant and with the ability to remove atrazine

-1 atrazine. Three strains of filamentous fungi were isolated and identified as Cladosporium cladosporioide, Rhizopus stolonifer and Penicillium purpurogenum. The isolates were tested for their ability to degrade atrazine in liquid medium containing 1.5 g L -1 of the herbicide as single source of carbon and nitrogen. In 15 days of culture, the isolated R. stolonifer showed a higher removal rate (73.75%), followed by P. purpurogenum (73.42%) and C. cladosporioides (68.42%), indicating a high possibility of using these microorganisms in the removal of atrazine in waters and effluents.