Fe2(SO4)3对活性污泥微生物活性的影响

为了解Fe₂(SO₄)₃作为絮凝剂对活性污泥中微生物活性的影响,向活性污泥系统中投加质量浓度为20、40、60、80,100 mg·L-1的Fe₂(SO₄)₃,反应4 h后测定活性污泥的脱氢酶活性、比耗氧速率(R_SOU)、胞外聚合物(EPS)及各组分含量,同时测定系统出水的COD等各项指标．结果表明:Fe₂(SO₄)₃质量浓度在20～60 mg·L-1时对活性污泥的脱氢酶活性、R_SOUEPS及各组分含量影响均不大,此时污水中COD、TP、UV₂₅₄等污染物随Fe₂(SO₄)₃质量浓度增加而有较大幅度去除．Fe₂(SO₄)₃质量浓度为80 mg·L-1时,污泥的脱氢酶活性、R_SOU、总EPS含量均明显下降．当Fe₂(SO₄)₃质量浓度增加到100 mg·L-1时,污泥的脱氢酶活性、R_SOU进一步受到抑制,而总EPS含量则大幅度提升．此时污水中COD、TP、UV₂₅₄等污染物去除率增加幅度变缓,SCOD及NH₃-N去除作用有所下降．     

低强度超声在低C/N污水处理中的应用

采用低C/N污水驯化的污泥为试验对象,以比耗氧速率和脱氢酶活性为表征,研究在超声频率为20 kHz,功率密度为0~0.35 W/mL、辐照时间为0~60 min处理后污泥活性的变化。结果显示,当采用声能密度和辐照时间为0.2 W/mL和12 min时,提高污泥活性的效果最显著。探究最佳条件下超声处理后0~10 h污泥活性的变化规律,发现辐照后5 h污泥活性达到最大,随后逐渐下降,直到8~10 h促进作用基本消失。采用辐照污泥比例分别为5%、15%和25%时,得出的最佳辐照污泥比例为15%,COD、氨氮、总磷出水浓度比对照组分别降低39.6%、37.1%、14.9%。     

Enzymatic and chemical synthesis of phosphatidylcholine regioisomers containing eicosapentaenoic acid or docosahexaenoic acid

Regioselective incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into phosphatidylcholine (PC) was carried out using enzymatic and chemical synthesis. Incorporation at the sn‐1 position was successfully achieved by lipase‐catalysed esterification of 2‐palmitoyl‐lysophosphatidylcholine (LPC), although in most cases, the enzymes incorporated EPA and DHA at lower rates than other fatty acids. For the incorporation of DHA, Candida antarctica lipase B was the only useful enzyme, while incorporation of EPA was efficiently carried out using either this enzyme or Rhizopus arrhizus lipase. The highest yields in the lipase‐catalysed reactions were obtained at the lowest water activity (close to 0). However, by carrying out the reactions at a higher water activity of 0.22, more EPA and DHA were incorporated. Esterification of 2‐palmitoyl‐LPC with pure EPA at this water activity converted 66 mol‐% of LPC to PC using Rhizopus arrhizus lipase as catalyst. When the fatty acid was DHA and the catalyst Candida antarctica lipase B, 45 mol‐% of PC was obtained. For incorporation of EPA and DHA at the sn‐2 position, phospholipase A₂ was used, but the reaction was very slow. Chemical coupling of 1‐palmitoyl‐LPC and EPA or DHA was more efficient, resulting in complete conversion of LPC.     

Effect of salt concentration on production of polyunsaturated fatty acids in <Emphasis Type="Italic">Thraustochytrium aureum</Emphasis> ATCC 34304

This study attempted to characterize the effects of NaCl and MgSO₄ as the primary components of sea salt affecting the yields of production of polyunsaturated fatty acids (PUFAs) by Thraustochytrium aureum ATCC 34304. Reductions in the NaCl concentration of the culture medium suppressed the formation of palmitic acid (PA, C16: 0) but enhanced the production of PUFAs, which induced an increase of the concentration of docosahexaenoic acid (DHA, C22: 6) up to 46.65% from 44.26%. MgSO₄ revealed a similar, yet more highly significant, effect on the fatty acids profile than NaCl. The yields of PUFAs and DHA showed maximum values such as 67.10% and 49.47%, respectively, at the concentration of 10 g L⁻¹ for NaCl and 0 g L⁻¹ for MgSO₄. However, the quantities of mono-and diunsaturated fatty acids, oleic acid (OA, C18: 1) and linoleic acid (LA, C18: 2) at the same concentrations, were compared with those of normal culture medium. Additionally, it was investigated that the increase of culture temperature reduced PUFAs contents but the reductions were recovered by the removal of MgSO₄ form the culture medium, which showed that concentration of salts and culture temperature affected independently the production of PUFAs in T. aureum.     

Applications of immobilized <Emphasis Type="Italic">Thermomyces lanuginosa</Emphasis> lipase in interesterification

The aim of this work was to investigate the catalytic functions of a new immobilized Thermomyces lanuginosa lipase in interesterification and to optimize the conditions of interesterification for the production of human milk fat substitutes (HMFS) containing n−3 PUFA by response surface methodology (RSM). Thermomyces lanuginosa lipase had an activity similar to that of immobilized Rhizomucor miehei lipase (Lipozyme RM IM) in the glycerolysis of sunflower oil, but the former had higher activity at a low reaction temperature (5°C). Thermomyces lanuginosa lipase was found to have much lower catalytic activity than Lipozyme RM IM in the acidolysis of sunflower oil with caprylic acid. However, the activity of T. lanuginosa lipase was only slightly lower than that of Lipozyme RM IM in the ester-ester exchange between tripalmitin (PPP) and the ethyl esters of EPA and DHA (EE). For this reason, the new immobilized T. lanuginosa lipase was used to produce HMFS from PPP by interesterification with EE. The optimization of major parameters was conducted with the assistante molar ratio of 5 (EE/PPP), a lipase load of 20 wt% (on substrates), and a reaction time of 20 h, with acyl incorporation up to 42%. The model generated significantly represented real relationships between the response (incorporation) and reaction parameters.     

Synthesis and characterization of poly(1,4-dihydroxyanthraquinone terephthalate)

A novel polymeric dye containing an anthraquinone ring was prepared by solution polycondensation. The molecule geometry was fully optimized on the basis of the AM1 method. The hydrogen bond was formed and retained coplanarity in the molecular structure. In its UV spectrum, a large hypsochromic shift and a hypochromic effect were observed due to polyesterification. The polymeric dye was also characterized by means of IR and TG. Its thermal degradation mechanism was elucidated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2246–2248, 2001     

Lipid content and fatty acid profile of Senegalese sole (Solea senegalensis Kaup, 1858) juveniles as affected by feed containing different amounts of plant protein sources

A growth trial with Senegalese Sole (Solea senegalensis Kaup, 1858) juveniles fed with diets containing increasing replacement levels of fishmeal by mixtures of plant protein sources was conducted over 12 weeks. Total fat contents of muscle, liver, viscera, skin, fins and head tissues were determined, as well as fatty acid profiles of muscle and liver (GC-FID analysis). Liver was the preferential local for fat deposition (5.5–10.8% of fat) followed by fins (3.4–6.7% fat). Increasing levels of plant protein in the diets seems to be related to increased levels of total lipids in the liver. Sole muscle is lean (2.4–4.0% fat), with total lipids being similar among treatments. Liver fatty acid profile varied significantly among treatments. Plant protein diets induced increased levels of C16:1 and C18:2 n−6 and a decrease in ARA and EPA levels. Muscle fatty acid profile also evidenced increasing levels of C18:2 n−6, while ARA and DHA remained similar among treatments. Substitution of fishmeal by plant protein is hence possible without major differences on the lipid content and fatty acid profile of the main edible portion of the fish – the muscle.     

Interspecific differences in omega-3 PUFA and contaminants explain the most variance in suggested Great Lakes’ fish consumption when risks/benefits are considered together

Contaminants and essential omega-3 fatty acids were analyzed in the fillets of 15 fish species from lakes Superior and Huron in order to estimate the risks and benefits of fish consumption. Additionally, literature data from lakes Ontario and Erie fish were used to provide an overall assessment for 24 fish species from the Canadian waters of the Great Lakes. The consumption advisory (based on contaminant levels) and EPA + DHA content (eicosapentanoic + docosahexanoic acid) were considered as a health risk and a health benefit, respectively.The differences in the risks and benefits of fish consumption were driven more by species than lake, indicating that within the Great Lakes advisories can focus on species rather than lakes to provide balanced risk-benefit estimates. Salmonines and coregonines had the highest EPA + DHA content; their mean EPA + DHA content ranged from 641 to 748 mg 100 g⁻¹ in salmonines, and from 340 to 728 mg 100 g⁻¹ in coregonines. The mean EPA + DHA content in Perciformes and Esociformes was 157–239 mg 100 g⁻¹ and 199–244 mg 100 g⁻¹, respectively. The species-specific consumption advisories were the most stringent for salmonines in all the lakes. For salmonines, the lake-specific advisories were the most stringent in lakes Ontario and Erie, although differences among lakes were small, indicating similar risks across all four lakes. Adherence to local species- and length-specific consumption advisories, in tandem with considering information on nutritional content, leads to evidence-based decisions regarding the optimum balance between risk and benefit with respect to fish consumption.     

Impact of smoking on the lipid fraction and nutritional value of seabob shrimp (Xiphopenaeus kroyeri, Heller, 1862)

The impact of smoking on the lipid fraction of seabob shrimp (Xiphopenaeus kroyeri, Heller, 1862) was evaluated by the formation of cholesterol oxides and changes in fatty acid composition and in nutritional quality. In addition, cholesterol and chloride contents, pH, and proximate composition were determined. Smoking reduced lipid and protein contents and increased ash and chloride concentrations, while the pH value remained constant. Despite the loss of 18:2n6 (53%), 20:4n6 (50%), 22:6n3 (49%), 20:5n3 (47%) and 18:1n9 (44%), the n6/n3 ratio did not change significantly. The index of atherogenic (0.82) and of thrombogenic (0.62) were low after smoking. Smoking also caused losses of cholesterol (27%) and 7β-hydroxycholesterol (50%), while 7-ketocholesterol and 7α-hydroxycholesterol contents remained constant.     

Improving antioxidant activity and nutritional components of Philippine salt-fermented shrimp paste through prolonged fermentation

The antioxidant activity and nutritional components of Philippine salt-fermented shrimp paste were improved through prolonged fermentation (90, 180, and 360 days). The antioxidant ability against 1,1-diphenyl-2-picryhydrazyl (DPPH) radical, hydrogen peroxide, and lipid peroxidation increased significantly with prolonged fermentation and were suggested to be related with the Maillard reaction products formed, as measured by the characteristic browning and fluorescent developments. Polyunsaturated fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the shrimp paste were not substantially damaged for 360 days, while free amino acid content dramatically increased at 90 days. However, excessive fermentation showed slight but significant decrease in free amino acids and increase in ammonia. These results suggest that properly prolonged fermentation would improve antioxidant ability and some nutritional value in the salt-fermented shrimp paste.