Low-cost fermentative medium for biosurfactant production by Streptococcus thermophilus A

Interest in biosurfactants has increased considerably in recent years, as they are potential candidates for many commercial applications in the petroleum, pharmaceuticals, biomedical and food processing industries. Biosurfactants have several advantages over chemical s urfactants including lower toxicity and higher biodegradability, and effectiveness at extreme temperatures or pH values. In spite of the advantages, fermentation must be cost competitive with chemical synthesis and many of the potential applications that have been considered for biosurfactants depend on whether they can be produced economically. The use of alternative molasses medium (sucrose content 20 g/L, supplemented with 3 g/L yeast extract and 5 g/L peptone) for biosurfactant production by Streptococcus thermophilus A was studied. Suitable models were established to describe the response of the experiments pertaining to glucose or sucrose consumption, cell growth and biosurfactant production. Conventional synthetic M17 broth was used as control experiments. The replacement of M17 broth by cheaper molasses medium resulted on an increase about 1.4 times in the mass of produced biosurfactant (mg) per gram cell dry weight and a 80% medium preparation costs reduction.In con clusion, the results obtained showed that molasses medium can be used as a relatively inexpensive and economical alternative to conventional synthetic medium for biosurfactant production by S. thermophilus A

Low-cost fermentative medium for biosurfactant production by probiotic bacteria

Potential use of alternative fermentative medium for biosurfactant production by Lactococcus lactis 53 and Streptococcus thermophilus A was studied. Suitable models were established to describe the response of the experiments pertaining to glucose, lactose or sucrose consumption, cell growth and biosurfactant production. Synthetic media MRS and M17 broth were used as control experiments. When the synthetic media were replaced by cheaper alternative media, as cheese whey and molasses, fermentations were carried out effectively with high yields and productivities of biosurfactant. An increase about 1.2–1.5 times in the mass of produced biosurfactant per gram cell dry weight and 60–80% medium preparation costs reduction were achieved, for both strains. In conclusion, the results obtained showed that supplemented cheese whey and molasses media can be used as a relatively inexpensive and economical alternative to synthetic media for biosurfactant production by probiotic bacteria, thus an attractive alternative as many of the potential applications for biosurfactants depend on whether they can be produced economically.Fundação para a Ciência e a Tecnologia (FCT

Enhancement of methane production from barley waste

Two different approaches were attempted to try and enhance methane production from an industrial waste composed of 100% barley, which results from production of instant coffee substitutes. In previous work, this waste was co-digested with an excess of activated sludge produced in the wastewater treatment plant located in same industrial unit, resulting in a very poor methane yield (25LCH4(STP)/ kgVSinitial), and low reductions in total solids (31%) and in volatile solids (40%). When the barley waste (BW) was subjected to alkaline hydrolysis pre-treatment before co-digestion with activated sludge, the methane production increased to 222LCH4(STP)/kgVSinitial and the total and volatile solids reductions increased to 67% and 84%, respectively. The second approach, followed in the present work, consisted of co-digestion with kitchen waste (40% BW, 60% kitchen waste). The methane production was 363LCH4(STP)/kgVSinitial and the total and volatile solids reductions were 61% and 67%, respectively.Fundação para a Ciência e a Tecnologia (FCT) - Project POCTI/1999/CTA/36524

Anaerobic digestion of coffee waste

The anaerobic co-digestion of five different by-products from instant coffee substitutes production was studied in mesophilic conditions. The co-substrate was the excess of sewage sludge from the wastewater treatment plant located in the same coffee factory. Four of the tested wastes produced methane in the range of 0.24-0.28 m³CH4(STP)/kgVSinitial . Reduction of 50-73% in total solids and 75-80% in volatile solids were obtained and the hydrolysis rate constants were in the range of 0.035-0.063 dֿ¹. After 40 days, one waste, composed of 100% barley, achieved a methane yield as low as 0.02 m³CH4(STP)/kgVSinitial and 31% and 40% total and volatile solids reduction, respectively,. Two different strategies were applied to enhance the biodegradability of this waste. An alkaline hydrolysis pre-treatment, that increased the methane production up to 0,22 m³CH4(STP)/kgVSinitial and the total and volatile solids reductions up to 67 and 84%, respectively. A co-digestion with kitchen waste, that increased the methane production up to 0,36 m³CH4(STP)/kgVSinitial and the total and volatile solids reductions up to 61 and 67%, respectively

Characterization of the wave bioreactor: residence time distribution

The high dose requirements of biopharmaceutics have led to the development of mammalian cell culture technologies to increase biomanufacturing capacity. Among them, disposable bioreactors are attracting attention, particularly the Wave bioreactor. This system induces an undulation movement to the culture, ensuring good mixing and oxygen transfer without shear damage, and requires no cleaning/sterilization, providing simpler operation and no cross-contamination. However, this new reactor still needs further characterization. In this sense, the residence time distribution (RTD) was evaluated, allowing the characterization of the mixing/flow and the comparison with ideal models and a commercial stirred tank reactor (STR). RTD was determined using methylene blue with a pulse input methodology, at three mammalian culture flow rates: low (L: 3.3x10-5 m3/h), intermediate (I: 7.9x10-5 m3/h), and high (H: 1.25x10-4 m3/h). Samples were taken and absorbance read at 660 nm. Results show that Wave behaviour approximates the ideal and experimental STR at flow L, but deviates from ideal models at flows I and H. The comparison of average residence time (tr) with time of passage (τ) provides a possible explanation for this non-ideality. For STR at all flows and Wave at flow H, tr was lower than τ, indicating dead zones inside the reactor. For Wave at flows L and I, tr was higher than τ, indicating short-circuiting. In conclusion, the choice of flow rate will strongly influence the behaviour of the Wave bioreactor. The use of a low flow seems to be a choice that provides behaviour closer to the ideal continuous STR model

Polysaccharide production and biofilm formation by Pseudomonas fluorescens: effects of pH and surface material

Although the synthesis of extracellular polysaccharides was first recognized in certain bacterial cultures a long time ago, its role in bacterial adhesion is still subject to some debate. Several fermentation batch cultures were performed under different conditions of pH (pH 7, maintained with NaOH and HCl; pH 7 in phosphate buffer, and without pH control) in order to study the relation between the production of extracellular polysaccharides and biofilm formation on polymeric slides suspended in the culture medium. The polymers used were polystyrene, polypropylene, polyethylene and poly(vinyl chloride). The maximum amount of exopolysaccharides in the culture medium occurs at pH 7, although slightly thicker biofilms seem to be formed when there is no pH control. The biofilms were analysed by scanning electron microscopy and by wavelength dispersion spectroscopy. Biofilm morphology seems to be much more dependent on the type of substratium than on the pH of the medium; for different pH values, a polymeric network can be more clearly observed on biofilms formed on all surfaces except poly(vinyl chloride)

Fouling by aqueous suspensions of magnetite particles: the effect of pH and ionic strength

Particles adhesion Is one of the fundamental steps in heat exchanger fouling. Surface Interactions are affected by a con siderable number of factors related to the nature of the surfaces Involved. and to the composition and dynamics of the fouling fluid. Although quantitative predictions of U1e rate of adhesion are still not feasible !n practical situations. the evaluation of the potential energy of Interaction between two surfaces "in each vicinity" can be a valuable tool for the qualitative assessment of the fouling tendencies. For that purpose experimental determination of the parameters characterizing the physico-chemical properties of the Interacting surfaces are required. The present paper reports studies on particulate fouling caused by aqueous suspensions of magnetite on copper surfaces. A series of experiments were carried out at different pH values in the range of 7.5 - 9.5. For each pH two distinct types of experiments were performed: In one case the pH was controlled wlth NaOH and In the other the pH controlling medium was Na2co3. Each run lasted 20 days and at the end the thi ckness of the deposits was measured by means of a micrometer coupled to an electrical circuit. The zeta potentials and surface tensions of the solids were measured and used !n the Interpretation of the results. which was carried out In terms of the DLVO Theory

The use of hot wire techniques in fouling tests: a word of awareness

Hot metal wires have been used in fouling tests, mainly when corrosion or chemical reaction is present. Most authors who have reported data obtained with hot wire techniques make no refence about the phenomenon related to the increase In surface area due to the accumulation of fouling layers. Yet this can cause problems of reverse insulation (critical radius), affecting the conclusions taken directly from the readouts. The aim of this paper is to discuss this problem and show through a few selected tases the Importance of this aspect in fouling resistance determinations using hot wire techniques

Efeitos de superfície na deposição de partículas de magnetite e de caulino sobre superfícies de cobre

A deposição de partículas em meta aquoso é regida pela ação combinada de diferentes interações superficiais e forças hidrodinâmicas. De entre o elevado número de factores que podem afectar as interações superficiais seleccionaram-se para estudo o efeito do pH e da força iónica do meio. Realizaram-se ensaios de deposição, sobre superfícies de cobre, com suspensões aquosas de magnetite e de caulino para valores de pH compreendidos entre 7 e 11. Para cada valor de pH foram feitos dois tipos distintos de ensaios: num caso o controlo do meio foi feito com NaOH, no outro com Na2CO3. Efectuaram-se ainda, outros ensaios em que, para um dado valor do pH, se alterou a força iónica do meio por adição de sais neutros (NaNO3 e NaC1). Para auxiliar a interpretação dos resultados obtidos nos ensaios anteriormente referidos, determinaram-se os potenciais zeta das partículas e do cobre em função do pH e calcularam-se as energias livres de adesão partícula-liquido-superfície. Os resultados obtidos têm sido analisados com base na teoria DLVO, com vista à compreensão dos mecanismos que lhe estão subjacentes. Embora não fosse previsível, pelo menos no caso do caulino, a melhor justificação para os resultados obtidos é conseguida admitindo que a interação entre as duplas camadas eléctricas de partículas e superfície se processa a potencial constante