Biosurfactant production by Rhodococcus erythropolis and its application to oil removal

The influence of different nutrients on biosurfactant production by Rhodococcus erythropolis was investigated. Increasing the concentration of phosphate buffer from 30 up through 150 mmol/L stimulated an increase in biosurfactant production, which reached a maximum concentration of 285 mg/L in shaken flasks. Statistical analysis showed that glycerol, NaNO3,MgSO4 and yeast extract had significant effects on production. The results were confirmed in a batchwise bioreactor, and semi-growth-associated production was detected. Reduction in the surface tension, which indicates the presence of biosurfactant, reached a value of 38 mN/m at the end of 35 hours. Use of the produced biosurfactant for washing crude oil-contaminated soil showed that 2 and 4 times the critical micellar concentration (CMC) were able to remove 97 and 99 percent of the oil, respectively, after 1 month of impregnation.

Sugar cane bagasse as feedstock for second generation ethanol production: part II: hemicellulose hydrolysate fermentability

Sugar cane bagasse is produced in Brazil as waste of the sugar and ethanol industries. This lignocellulosic material is a potential source for second-generation ethanol production; however a pretreatment stage is essential, which aims at removing the hemicellulose component by disorganizing the lignocellulosic complex. In this work sugar cane bagasse was pretreated by diluted acid hydrolysis resulting in xylose-rich hydrolysates, which could be fermented to ethanol by a strain of the yeast Pichia stipitis. Statistical approach was used to investigate the effects of factors associated with the diluted acid hydrolysis process (acid concentration, solid:liquid ratio and time of exposure) on the fermentability of different hydrolysates. The statistical analysis was useful for determining the effects of the individual factors and their interactions on the response variables. An acid concentration of 1.09 percent (v/v), a solid:liquid ratio of 1:2.8 (g:ml), and an exposure time of 27 min were established and validated as the optimum pretreatment conditions for ethanol production from hemicellulose hydrolysates of sugar cane bagasse. Under these conditions, a hydrolysate with 50 g/l of xylose, 6.04 g/l of acetic acid, 0.55 g/l of hydroxylmethylfurfural and 0.09 g/l of furfural was obtained and its fermentation yielded roughly 20 g/l of ethanol in 40 hrs.

Sugar cane bagasse as feedstock for second generation ethanol production: part I: diluted acid pretreatment optimization

Tons of sugar cane bagasse are produced in Brazil as waste of the sugar and ethanol industries. This lignocellulosic material is a potential source for second-generation ethanol production. Diluted acid hydrolysis is one of the most efficient pretreatments for hemicellulosic solubilization. The hydrolysate obtained is rich in xylose, which can be converted to ethanol by Pichia stipitis. This work used a statistical approach and the severity factor to investigate the effects of factors associated with the diluted acid hydrolysis process (acid concentration, solid:liquid ratio and time of exposure) on various response variables (xylose concentration, hydrolysis yield, inhibitor concentration and hydrolysate fermentability). The severity factor had a strong influence on the generation of inhibitors. The statistical analysis was useful for determining the effects of the individual factors and their interactions on the response variables. An acid concentration of 1.09 percent (vv), an S:L ratio of 1:2.8 (g:ml), and an exposure time of 27 min were established and validated as the optimum pretreatment conditions for the generation of hydrolysates with high xylose concentration and low contents of inhibitors. In such conditions, hydrolysate with 50 g/l of xylose was obtained.

Simultaneous saccharification and fermentation process of different cellulosic substrates using a recombinant Saccharomyces cerevisiae harbouring the beta-glucosidase gene

In Brazil, the production of ethanol from sugarcane produces large amounts of lignocellulosic residues (bagasse and straw), which have been driving research and development for the production of second generation ethanol. In the present work, a recombinant Saccharomyces cerevisiae strain expressing the beta-glucosidase gene from Humicola grisea was used for ethanol production from three different cellulosic sources by simultaneous saccharification and fermentation. Initially, a enzymatic pre-hydrolysis step was done with a solid:liquid ratio of 1:4, and an enzymatic load of 25 filter paper activity (FPU).g-1 of cellulosic substrate. Using sugarcane bagasse pretreated cellulignin, crystalline cellulose and carboxymethyl cellulose, 51.7 g L-1, 41.7 g L-1 and 13.8 g L-1 of ethanol was obtained, respectively, at the end of 55 hrs of fermentation. The highest ethanol productivity (0.94 g L-1 hrs-1) was achieved using sugarcane bagasse pretreated cellulignin. The use of a recombinant S. cerevisiae led to extremely low glucose concentrations when compared to other works reported in literature.

Biodegradation of stored jet fuel by a Nocardia sp. isolated from contaminated soil

The aim of this study was to investigate the potential of degradation of an autochthonous bacterial strain, isolated from petroleum derivatives contaminated soil samples against jet fuel hydrocarbons. The autochthonous bacterial strain was characterized as Nocardia sp. Evaluation of their degrading abilities was carried out by presumptive assays as redox indicator test and by observations of surface tension decreases in aqueous medium. Degradation of jet fuel hydrocarbons was evaluated by chromatographic methods. Experiments were performed in flasks at two biostimulation rates. A bacterial strain of Pseudomonas aeruginosa UFPEDA 39 was utilized as a reference microorganism. The bacterial strain, identified as Nocardia sp, demonstrate high ability to degrade jet fuel compounds as well as to produce surface active compounds when compared to the reference microrganism.

O presente estudo objetivou a investigação da capacidade degradadora de uma linhagem bacteriana autóctone (isolada de amostras de solo contaminadas com derivados de petróleo) contra hidrocarbonetos de querosene de aviação. A linhagem foi caracterizada como Nocardia sp. A avaliação do seu potencial degradador deu-se realizada mediante testes com indicador redox e observações na redução da tensão superficial na fase aquosa. A degradação do querosene foi avaliada por métodos cromatográficos. Os experimentos foram realizados utilizando-se duas taxas de bioestímulo. Uma linhagem bacteriana Pseudomonas aeruginosa UFPEDA 39 foi utilizada como referência. A linhagem autóctone demonstrou alta eficiência na degradação de hidrocarbonetos do querosene bem como para produzir compostos ativos de superfície quando comparada com a linhagem de referência.

Evaluation of cell recycle on Thermomyces lanuginosus Xylanase A production by Pichia pastoris GS 115.

This work aims to evaluate cell recycle of a recombinant strain of Pichia pastoris GS115 on the Xylanase A (XynA) production of Thermomyces lanuginosus IOC-4145 in submerged fermentation. Fed-batch processes were carried out with methanol feeding at each 12 h and recycling cell at 24, 48, and 72 h. Additionally, the influence of the initial cell concentration was investigated. XynA production was not decreased with the recycling time, during four cell recycles, using an initial cell concentration of 2.5 g/L. The maximum activity was 14,050 U/L obtained in 24 h of expression. However, when the initial cell concentration of 0.25 g/L was investigated, the enzymatic activity was reduced by 30 and 75% after the third and fourth cycles, respectively. Finally, it could be concluded that the initial cell concentration influenced the process performance and the interval of cell recycle affected enzymatic production.

RSM analysis of the effects of the oxygen transfer coefficient and inoculum size on the xylitol production by Candida guilliermondii.

Biotechnology production of xylitol is an excellent alternative to the industrial chemical process for the production of this polyalcohol. In this work the behavior of Candida guilliermondii yeast was studied when crucial process variables were modified. The K(L)a (between 18 and 40/h) and the initial cell mass (between 4 and 10 g) were considered as control variables. A response surface methodology was applied to the experimental design to study the resulting effect when the control variables were modified. A regression model was developed and used to determine an optimal value that was further validated experimentally. The optimal values determined for K(L)a and X(0) were 32.85/h and 9.86 g, respectively, leading to maximum values for productivity (1.628 g/h) and xylitol yield (0.708 g/g).

Biosurfactant production by Rhodococcus erythropolis grown on glycerol as sole carbon source.

The production of biosurfactant by Rhodococcus erythropolis during the growth on glycerol was investigated. The process was carried out at 28 degrees C in a 1.5-L bioreactor using glycerol as carbon source. The bioprocess was monitored through measurements of biosurfactant concentration and glycerol consumption. After 51 h of cultivation, 1.7 g/L of biosurfactant, surface, and interfacial tensions values (with n-hexadecane) of 43 and 15 mN/m, respectively, 67% of Emulsifying Index (E24), and 94% of oil removal were obtained. The use of glycerol rather than what happens with hydrophobic carbon source allowed the release of the biosurfactant, originally associated to the cell wall.

Production and properties of the cellulase-free xylanase from Thermomyces lanuginosus IOC-4145

In recent years, xylanases have expanded their use in many processing industries, such as pulp and paper, food and textile. Thermomyces lanuginosus IOC-4145 was able to produce a very high level of cellulase-free xylanase in shaken cultures using corncob as substrate (500 U/ml). An optimization of the medium composition in submerged fermentation was carried out aiming at a low cost medium composition for enzyme production. Statistical experiment design ws employed for this purpose, pointing out corncob as the most important parameter, which affects enzyme production. Additionally, the influence of several chemicals on zulanase activity was investigated in the crude extract. A slight stimulation of the enzyme (5-15 percent) was achieved with NaCl and urea, both at 3 mM of concentration. On the other hand, dithiothreitol and ß-mercaptoethanol at a molarity of 5mM have caused a strong stimulation of the enzyme (40-53 percent). The crude xylanase displayed appreciable thermostability, retaining almost 50 percent of activity during 24 hours of incubation at 50oC; about 50 percent of activity was present at 60oC even after4 hours of incubation. The enzyme also exhibited good storage stability at û20oC without any stabilizing agent.

A chemically defined medium for production of actinomycin D by Streptomyces parvulus / A chemically defined medium for production of actinomycin D by Streptomyces parvulus

Um meio quimicamente definido composto de D (+) FRUTOSE, L (-) treonina, K2HPO4, MgSO4.7H2O, ZnSO47H2O, CaCl2.2H2o, FeSO4.7H2O e água deionizada, foi desenvolvido para maximizar a síntese de actinomicina D pelo Streptomyces parvulus DAUFPE3124. o meio proposto resultou numa concentraçäo antibiótica máxima de 133mg/L enquanto que no meio inicial a produçäo antibiótica foi baixa, näo ultrapassando 43mg/L

Modeling of the production of xylitol from d-xylose in a batch and continuous membrane bioreactor

This work presents a mathematical model that describes of the behavior of the main variable involved in the continuous bioconversion of xylose to xylitol by Candida guilliermondii in a stirred-tank bioreactor with total cell recycle, a promising process to obtain this polyol because it increases productivity in function of the high cellular density. The fermentation system was modeled considering cellular mass, xylose, xylitol and dissolved oxygen concentrations, as well as xylose reductase enzymatic activit as dependent variables. The model is based on the assumption of the intra/extracellular xylitol transport and it is able to represent inhibition by xylose on the main intracellular reaction (conversion of xylose to xylitol by xylose reductase) as well as the influence of the oxygen limitation in all steps of the bioconversion. The results of the mathamatical model simulation were compared to experimental data. The model represents quite well the yeast performance in the production of xylitol.

Thermal stability of xylanases produced by "Aspergillus awamori"

The effect of temperature on the activity and stability of endoxylanase and (beta)-xylosidase from "Aspergillus awamori" was investigated. The growth of "A. awamori" in milled sugar cane bagasse produced predominantly extracellular endoxylanase (30 U/ml) and lower amounts of (beta)-xylosidase (1.3 U/ml). Grown in sugar cane bagasse as the principal carbon source, the microorganism produced a quite stable (beta)-xylosidase in a temperature range of 35-55ºC, but it exhibited a lower thermostable endoxylanase. The thermostability of endoxylanase was enhanced through addition of polyhydric alcohols, mainly 2 M xylitol and sorbitol solutions. Particular stability upon storage (100(per cent)) was found for endoxylanase at -4ºC for 165 days. Yet for (beta)-xylosidase, and activity decrease of approximately 20(per cent) was observed during the first 15 days of storage, maintaining roughly 75(per cent) of initial activity until the end of the experiment.

Effect aeration on biodegradation of petroleum waste

Large amaounts of oily sludge are generated as residues by the oil industry, representing a real problem for refineries. This work studied the technical viability of treating oily aludge biologically, through stimulation of native microorganisms, at bench scale. Such microorganisms were able to grow in a medium containing oily sludge as the only carbon and energy source. Two oily sludge concentrations were studied, 5(per cent) (v/v) and 10 (per cent) (v/v), with a C:N ratio of 100:1. Higher microbial populations were observed in the first case. Substrate inhibition and/or toxic effect took place in the second case. The importance of aeration on the microbial activity and on the biodegradation of the residue was ascertained. In terms of n-paraffins, pristane and phytane consumption, maximum global efficiency of the genus "Pseudomonas sp." predominated. Two yeast species were also identified and two filamentous fungi were isolated.

The ionic character of the environment in the flocculation of Pichia sptipitis

Embora células de uma linhagem floculante de Pichia stipitis tornaram-se completamente dispersas após lavagens com água destilada, essas mesmas células reflocularam quando suspensas em soluçöes de componentes individuais do meio. A força iônica de tais soluçöes foi suposta ser a causa primária do fenômeno. A medida da condutividade elétrica mostrou ser um modo prático de avaliar a força iônica do meio ambiente. A floculaçäo foi mais intensa quanto maior o valor da condutividade elétrica das soluçöes, atingindo o seu ótimo e permanecendo praticamente constante para valores de condutividade elétrica acima de 1000s. Isto sugere que reduçäo de cargas associadas a mudanças conformacionais na estrutura das proteínas da parede celular tenham sido responsáveis pela agregaçäo de células. Adicionalmente, uma diminuiçäo da condutividade elétrica do meio, através de diálise, reduziu a habilidade das células de flocular. O caráter iônico do meio mostrou ser um importante fator influenciador na floculaçäo