Removal of low molecular weight phenols from olive oil mill wastewater using microalgae

The treatment of olive oil mill wastewater (OMW) with two phenol resistant algae, Ankistrodesmus braunii and Scenedesmus quadricauda, showed a limited reduction of phenol content after 5 d of treatment, irrespective of algal concentration. Otherwise, cultures of both algae, grown in the dark, degraded over 50% of the low molecular weight phenols contained in OMW, but they were not completely removed, but were biotransformed into other non-identified, aromatic compounds.     

Biodegradation of p-nitrophenol by microalgae

A study was made on the use of a mixed microalgal consortium to degrade p-nitrophenol. The consortium was obtained from a microbial community in a waste container fed with the remains and by-products of medium culture containing substituted aromatic pollutants (nitrophenols, chlorophenols, fluorobenzene). After selective enrichment with p-nitrophenol (p-NP), followed by an antibiotic treatment, an axenic microalgal consortium was recovered, which was able to degrade p-nitrophenol. At a concentration of 50 mg L^–1, total degradation occurred within 5 days. Two species, Chlorella vulgaris var. vulgaris f. minuscula and Coenochloris pyrenoidosa, were isolated from the microalgal consortium. The species were able to accomplish p-NP biodegradation when cultured separately, although Coenochloris pyrenoidosa was more efficient, achieving the same degradation rate as the original axenic microalgal consortium. When Coenochloris pyrenoidosa was associated with Chlorella vulgaris in a 3:1 ratio, complete removal of the nitro-aromatic compound occurred within three days. This is apparently the first report on the degradation of a nitro-aromatic compound by microalgae.     

微藻规模化培养研究进展

微藻作为地球上最古老的物种之一,其诞生可追溯到35亿多年前.微藻的种类十分丰富,形态也多种多样.微藻一般都含有叶绿体,因此可进行光合作用,有研究表明微藻固定CO2的能力是陆地植物的10倍.微藻以其丰富的代谢产物及独特的生理特性在可再生能源、生物医药、食品工业和环境监测等方面有着广泛的应用.然而如何在控制成本的前提下对微...     

Hydrogen production by microalgae

The production of H₂ gas from water and sunlightusing microalgae, `biophotolysis', has been a subjectof applied research since the early 1970s. A numberof approaches have been investigated, but most provedto have fundamental limitations or requireunpredictable research breakthroughs. Examples areprocesses based on nitrogen-fixing microalgae andthose producing H<sub>2</sub> and O<sub>2</sub> simultaneously fromwater (`direct biophotolysis'). The most plausibleprocesses for future applied R & D are those whichcouple separate stages of microalgal photosynthesisand fermentations (`indirect biophotolysis'). Theseinvolve fixation of CO₂ into storagecarbohydrates followed by their conversion to H₂by the reversible hydrogenase, both in dark andpossibly light-driven anaerobic metabolic processes. Based on a preliminary engineering and economicanalysis, biophotolysis processes must achieve closeto an overall 10% solar energy conversion efficiencyto be competitive with alternatives sources ofrenewable H₂, such as photovoltaic-electrolysisprocesses. Such high solar conversion efficiencies inphotosynthetic CO₂ fixation could be reached bygenetically reducing the number of light harvesting(antenna) chlorophylls and other pigments inmicroalgae. Similarly, greatly increased yields ofH₂ from dark fermentation by microalgae could beobtained through application of the techniques ofmetabolic engineering. Another challenge is toscale-up biohydrogen processes with economicallyviable bioreactors.Solar energy driven microalgae processes forbiohydrogen production are potentially large-scale,but also involve long-term and economically high-riskR&D. In the nearer-term, it may be possible tocombine microalgal H₂ production with wastewatertreatment.     

Biodegradation of chlorophenol mixtures by Pseudomonas putida

The dynamic growth behavior of Pseudomonas putida has been studied when resting calls were inoculated into a growth medium containing inhibitory concentrations of mixtures of phenol and monochlorophenols. Resting cells inoculated into single carbon substrate media did not demonstrate enhanced cell lysis by any of the phenol substrates. The apprarent death rate was reduced as the concentrations of phenol or chlorophenols were increased. This behavior was modeled by employing a constant specific death rate (k(d) = 0.0075 h(-1)) and assuming all organic species result in a lag-phase, specific growth rate which may be larger or smaller than k(d).Logarithmic biomass growth on pure monochlorophenols did not occur within 2 weeks after inoculation. Logarithmic growth phases were only observed when the monochlorophenols were cometabolized with phenol. The delay time over which the lag phase exists increased exponentially with phenol concentration and linearly with monochlorophenol concentration. The log growth yield coefficient decreased linearly with monochlorophenol concentration.The lag-phase, specific growth rate was found to decrease exponentially with the concentration of monochlorophenols. This resulted in a 50% lag growth rate inhibition for both 3- and 4-chlorophenol of 9 ppm and for 2-chlorophenol of only 2 ppm. The new, empirical correlations are shown to closely model the complete lag and log growth behavior ot P. putida on phenol and chlorophenol mixtures. (c) 1992 John Wiley & Sons, Inc.     

Attenuation of 4-I-phenol-enhanced chemiluminescence by non-enhancer phenols

The intensity of 4-I-phenol-enhanced chemiluminescence from the luminol-H₂O₂-horseradish peroxidase system is markedly attenuated in the presence of low concentrations of non-enhancer phenols. Under the conditions studied, the effect is not associated with competition between 4-I-phenol and non-enhancer phenol for the enzyme intermediates, Compounds I and II, but involves a competition between non-enhancer phenol and luminol most probably for the 4-I-phenoxy radical.     

Biodegradation of plasticizers by Rhodococcus rhodochrous

Rhodococcus rhodochrous was grown in the presence of oneof three plasticizers: bis 2-ethylhexyl adipate (BEHA), dioctyl phthalate (DOP) ordioctyl terephthalate (DOTP). None of the plasticizers were degraded unless anothercarbon source, such as hexadecane, was also present. When R. rhodochrous was grownwith hexadecane as a co-substrate, BEHA was completely degraded and the DOP was degraded slightly. About half of the DOTP was degraded, if hexadecane were present.In all of these growth studies, the toxicity of the media, which was assessed usingthe Microtox assay, increased as the organism degraded the plasticizer. In each case, therewas an accumulation of one or two intermediates in the growth medium as the toxicityincreased. One of these was identified as 2-ethylhexanoic acid and it was observed forall three plasticizers. Its concentration increased until degradation of the plasticizershad stopped and it was always present at the end of the fermentation. The other intermediatewas identified as 2-ethylhexanol and this was only observed forgrowth in the presence of BEHA. The alcohol was observed early in the growth studies with BEHA and haddisappeared by the end of the experiment. Both the 2-ethylhexanol and 2-ethylhexanoicacid were shown to be toxic and their presence explained the increase of toxicity asthe fermentations proceeded. The appearance of these intermediates was consistent with similar degradation mechanisms for all three plasticizers involving hydrolysisof the ester bonds followed by oxidation of the released alcohol.     

Biodegradation of dibenzothiophene by thermophilic bacteria

Anaerobic microbial biodegradation of dibenzothiophene (DBT) was studied using thermophilic bacteria obtained from crude oil. A mixed culture was obtained that degraded 98% of DBT at 0.5 mg ml^–1 at 65 °C over 15 days both in the presence and in the absence of Methyl Viologen.     

Biodegradation of phenols by the alga Ochromonas danica.

The eukaryotic alga Ochromonas danica, a nutritionally versatile, mixotrophic chrysophyte, grew on phenol as the sole carbon source in axenic culture and removed the phenol carbon from the growth medium. Respirometric studies confirmed that the enzymes involved in phenol catabolism were inducible and that the alga oxidized phenol; the amount of oxygen consumed per mole of oxidized substrate was approximately 65% of the theoretical value. [U-14C]phenol was completely mineralized, with 65% of the 14C label appearing as 14CO2, approximately 15% remaining in the aqueous medium, and the rest accounted for in the biomass. Analysis of the biomass showed that 14C label had been incorporated into the protein, nucleic acid, and lipid fractions; phenol carbon is thus unequivocally assimilated by the alga. Phenol-grown cultures of O. danica converted phenols to the corresponding catechols, which were further metabolized by the meta-cleavage pathway. This surprising result was rigorously confirmed by taking the working stock culture through a variety of procedures to check that it was axenic and repeating the experiments with algal extracts. This is, as far as is known, the first definitive identification of the meta-cleavage pathway for aromatic ring degradation in a eukaryotic alga, though its incidence in other eukaryotes has been (infrequently) suggested.     

Biodiversity and application of microalgae

The algae are a polyphyletic, artificial assemblage of O₂-evolving, photosynthetic organisms (and secondarily nonphotosynthetic evolutionary descendants) that includes seaweeds (macroalgae) and a highly diverse group of microorganisms known as microalgae. Phycology, the study of algae, developed historically as a discipline focused on the morphological, physiological and ecological similarities of the subject organisms, including the prokaryotic bluegreen algae (cyanobacteria) and prochlorophytes. Eukaryotic algal groups represent at least five distinct evolutionary lineages, some of which include protists traditionally recognized as fungi and protozoa. Ubiquitous in marine, freshwater and terrestrial habitats and possessing broad biochemical diversity, the number of algal species has been estimated at between one and ten million, most of which are microalgae. The implied biochemical diversity is the basis for many biotechnological and industrial applications.     

酰胺生物降解机制的分子模拟研究

为探索酰胺生物降解酶的微观降解机制,用分子对接的方法模拟了酰胺与酰胺酶的相互作用,得到其复合物结构的理论模型,根据打分函数最低原则筛选出的RhAmidase与L-Methioninamide之间最佳构象打分函数为-86.741 9,二次打分函数为-76.022 4。同时,应用LPC/CSU Server研究了最佳构象的相互作用情况,结果表明,酰胺与酰胺酶之间以疏水作用数量最多,酰胺酶的ARG256 A、LEU353 A、TYR346 A、ARG225 A、THR218 A和PRO222 A在催化过程中起到了重要作用。     

Biodegradation of phenol and cresol isomer mixtures by Arthrobacter

The Arthrobacter species can degrade phenol, o-cresol and p-cresol much faster (as reflected in high specific growth rates) than other microbes which are reported to degrade toxic compounds. In mixtures, phenol and p-cresol mutually inhibited each other; the inhibition constants show that phenol degradation is strongly inhibited in the presence of p-cresol rather than reverse. o-Cresol enhanced phenol degradation marginally but o-cresol degradation was not affected by the presence of phenol.     

Effect of light/dark cycles on wastewater treatments by microalgae

Chlorella kessleri was cultivated in artificial wastewater using diurnal illumination of 12 h light/12 h dark (L/D) cycles. The inoculum density was 10⁵ cells/mL and the irradiance in light cycle was 45 μmol m² s⁻¹ at the culture surface. As a control culture, another set of flasks was cultivated under continuous illumination. Regardless of the illumination scheme, the total organic carbon (TOC) and chemical oxygen demand (COD) was reduced below 20% of the initial concentration within a day. However, cell concentration under the L/D lighting scheme was lower than that under the continuous illuminating scheme. Thus the specific removal rate of organic carbon under L/D cycles was higher than that under continuous illumination. This result suggested thatC. kessleri grew chemoorganotrophically in the dark periods. After 3 days, nitrate was reduced to 136.5 and 154.1 mg NO₃ ⁻-N/L from 168.1 mg NO₃ ⁻-N/L under continuous illumination and under diurnal cycles, respectively. These results indicate nitrate removal efficiency under continuous light was better than that under diurnal cycles. High-density algal cultures using optimized photobioreactors with diurnal cycles will save energy and improve organic carbon sources removal.     

活体微藻吸附水体中Cd2+的性能特征

【目的】藻类对重金属吸附和吸收是重金属进入食物链的重要渠道之一。研究活体微藻对水体中Cd~(2+)的吸附性能和吸附机理,旨在为Cd~(2+)等重金属离子进入水体后的去向及去除提供理论依据。【方法】选取地表水普遍存在的4种微藻:钝顶螺旋藻(Spirulina platensis)、铜绿微囊藻(Microcystis aeruginosa)、四尾栅藻(Scenedesmus quadricauda)和小球衣藻(Chlamydomonas microsphaera)作为试验材料,通过室内模拟实验,利用Langmuir、Freundlich和Dubinin-Radushkevich(D-R)3种等温吸附模型,研究4种活体微藻对Cd~(2+)的吸附规律及吸附参数。【结果】4种微藻对水体Cd~(2+)吸附均可以用Langmuir、Freundlich和D-R模型描述,其中用Langmuir模型拟合钝顶螺旋藻、Freundlich模型拟合小球衣藻、D-R模型拟合铜绿微囊藻和四尾栅藻的吸附效果最佳。四尾栅藻对Cd~(2+)的吸附量最高,而钝顶螺旋藻对Cd~(2+)的吸附量最低,但与Cd~(2+)的亲和力最强,4种微藻吸附Cd~(2+)主要是以离子代换为主的化学吸附。【结论】微藻对Cd~(2+)均有较强的吸附能力,会引起以微藻为食的水生动物Cd~(2+)富集;微藻也是去除水体Cd~(2+)的潜在吸附剂原料。     

微藻废水生物处理技术研究进展

微藻因生长速率快、细胞脂质含量高及具有生物隔离二氧化碳能力,已作为新一代生物质能源受到广泛关注.然而,投入大量淡水资源并需在生长期间持续提供营养物质已成为规模化培育微藻的主要障碍.将微藻培育系统与废水处理相结合是经济可行的污水资源化方案.基于微藻生长期间对氮磷等营养物质的利用机制,本文综述了微藻在各类废水生物处理过程中的应用情况,着重分析了其对废水中有机与无机化合物、重金属以及病原体的去除或抑制能力.同时,考察了废水初始营养物浓度、光照、温度、pH与盐度以及气体交换量等环境因素对微藻生长代谢的影响.此外,结合微藻规模化应用所面临的问题,对微藻废水处理技术的应用前景及发展方向进行了展望,旨在为水生态系统的建设与管理提供参考.     

芫菁寄生菌降解斑蝥素

选用2种芫菁的寄生菌——球孢白僵菌Beauveria bassiana和曲霉Aspergillus sp.,进行斑蝥素的抑菌试验和对斑蝥素的降解试验。结果表明:斑蝥素对这2种真菌没有抑制作用,球孢白僵菌可以有效地降解斑蝥素,降解率为90.45%,而曲霉不能降解斑蝥素。     

Biodegradation of alkylpyridines by bacteria isolated from a polluted subsurface

Ten bacterial strains were isolated fromalkylpyridine polluted sediments 7.6 m below thesurface. These strains were able to degrade 11different alkylpyridine isomers. Degradation ratesdepended on number and position of the alkyl group. Isomers with an alkyl group at position 3 were moreresistant to microbial attack. Of the 10 strains, 6isolates were selected for detailed study. Theseisolates mineralized the isomers to CO₂,NH₄ ⁺, and biomass. All strains weregram-negative rods with a strict aerobic metabolism. Characterization of physiological and biochemicalproperties revealed similarity between strains. Eeachstrain however, had a limited substrate range whichenabled it to degrade no more than 2 to 3 compounds ofthe 14 alkylpyridine isomers tested. Examination ofthe genetic variability among cultures with therandomly amplified polymorphic DNA technique revealedhigh levels of genomic DNA polymorphism. The highestsimilarity between 2 strains (0.653) was observedbetween 2-picoline and 3-picoline degrading cultures. The molecular basis of the differences in substratespecificity is under investigation.     

A mechanistic model of photosynthesis in microalgae

A dynamic model of photosynthesis is developed, accounting for factors such as photoadaptation, photoinhibition, and the "flashing light effect." The model is shown to explain the reported photosynthesis-irradiance responses observed under various conditions (constant low light, constant intense irradiance, flashing light, diurnal variation in irradiance). As significant distinguishing features, the model assumes: (1) The stored photochemical energy is consumed in an enzyme-mediated process that obeys Michaelis-Menten kinetics; and (2) photoinhibition has a square-root dependence on irradiance. Earlier dynamic models of photosynthesis assumed a first-order dependence of photoinhibition on irradiance and different kinetics of consumption of the stored energy than used in this work. These earlier models could not explain the photosynthesis-irradiance behavior under the full range of irradiance scenarios-a shortcoming that is overcome in the model developed in this work.     

Heterotrophic production of ascorbic acid by microalgae

An aerobic fermentation process has been developed for the production of L-ascorbic acid (vitamin C). After an extensive screening program for microorganisms capable of heterotrophically synthesizing L-ascorbic acid, a unicellular green microalga,Chlorella pyrenoidosa, was selected. This organism has a number of characteristics that recommend it as an industrial organism: (1) it can double every 3.5 h when growing aerobically in the dark on a glucose-minimal salts medium; (2) its small size and tough cell wall make it very insensitive to shear, allowing very high impeller velocities; (3) it can be grown to 100 g L^–1 cell dry weight; (4) it is readily mutable by classical mutagenesis techniques; and (5) it has efficient growth kinetics with respect to yield of cell mass on glucose and oxygen. Fermentation process development and classical strain improvement have resulted in a greater than 70-fold increase in intracellular ascorbic acid concentration compared to the parent strainC. pyrenoidosa UTEX 1663. The process is compatible with existing industrial fermentation technology and equipment and is described in U.S. Patent 5,001,059. Patents have been submitted for a process in which the ascorbic acid accumulates extracellularly.