Efficient concomitant production of lipids and carotenoids by oleaginous red yeast <Emphasis Type="Italic">Rhodotorula glutinis</Emphasis> cultured in palm oil mill effluent and application of lipids for biodiesel production

Rhodotorula glutinis TISTR 5159 is oleaginous red yeast that accumulates both lipids and carotenoids. It was cultured in palm oil mill effluent (POME) with only the addition of ammonium sulfate and Tween 20 as a suitable nitrogen source and surfactant, respectively. Response surface methodology (RSM) was applied to optimize initial chemical oxygen demand (COD) in POME, C/N ratio, and Tween 20 concentration for concomitant production of lipids and carotenoids. Among three investigated factors, C/N ratio contributed a significant effect upon lipid and carotenoids production. Analysis of response surface plots revealed that the optimum C/N ratio for the biomass was 140, while that for lipid content and carotenoids were higher at 180 and 170, respectively. The high level of the nitrogen source (with a low C/N ratio) enhanced the biomass, making the accumulation of lipids and carotenoids less preferable. Hence, the two-stage process was attempted as an optimal way for cell growth in the first stage and product accumulation in the second stage. The lipid yield and carotenoid production obtained in the two-stage process were higher than those in the one-stage process. In the semi-continuous fermentation, R. glutinis TISTR 5159 accumulated high lipid content and produced a considerably high concentration of carotenoids during long-term cultivation. Additionally, efficient COD removal by R. glutinis TISTR 5159 was observed. The biodiesel produced from yeast lipids was composed mainly of oleic and palmitic acids, similar to those from plant oil.     

粘红酵母和酿酒酵母联合处理味精废水

为了解决味精废水中高NH4+浓度抑制油脂微生物的生长和油脂积累问题,采用粘红酵母和酿酒酵母联合处理味精废水的方法:首先利用酿酒酵母降解味精废水(MSG)中NH4+,然后将处理后的废水进一步发酵培养合成油脂。研究结果表明:用经酿酒酵母预处理过的味精废水作为粘红酵母的培养基发酵时,粘红酵母的生物量为33.3 g/L,油脂产率为18.16%,COD降解率为50.6%,NH4+的降解率为93.9%。比粘红酵母单独处理味精废水,NH4+的降解率提高了6.14倍,生物量、油脂产率和COD降解率分别提高了8.1%、30.06%和9.58%。     

Regulation of docosahexaenoic acid production by Schizochytrium sp.: effect of nitrogen addition

Docosahexaenoic acid (DHA) percentage in total fatty acids (TFAs) is an important index in DHA microbial production. In this study, the change of DHA percentage in response to fermentation stages and the strategies to increase DHA percentage were investigated. Two kinds of conventional nitrogen sources, monosodium glutamate (MSG) and ammonium sulfate (AS), were tested to regulate DHA synthesis. Results showed that MSG addition could accelerate the substrate consumption rate but inhibit lipid accumulation, while AS addition could increase DHA percentage in TFAs effectively but extend fermentation period slightly. Finally, the AS addition strategy was successfully applied in 7,000-L fermentor and DHA percentage in TFAs and DHA yield reached 46.06 % and 18.48 g/L, which was 19.54 and 17.41 % higher than that of no-addition strategy. This would provide guidance for the large-scale production of the other similar polyunsaturated fatty acid, and give insight into the nitrogen metabolism in oil-producing microorganisms.     

Effect of nitrogen concentration on the activity of manganese peroxidase ofPhanerochœte chrysosporium

Manganese peroxidase as an extracellular enzyme is produced by the white rot fungusPhanerochœte chrysosporium under nutrient nitrogen or carbon limitation. The effect of nitrogen concentration on the activity of manganese peroxidase was studied using ammonium nitrate andl-asparagine as nitrogen sources. The highest activity of the enzyme was observed in cultures grown in a medium containing 75 mg/L ammonium nitrate and 0.15 g/Ll-asparagine. Manganese peroxidase was not detectable in cultures grown in the presence 0.5 g/L ammonium nitrate and 1 g/Ll-asparagine.     

Enhanced docosahexaenoic acid production by reinforcing acetyl-CoA and NADPH supply in <Emphasis Type="Italic">Schizochytrium</Emphasis> sp. HX-308

Docosahexaenoic acid (DHA) production in Schizochytrium sp. HX-308 was evaluated by detecting enzymatic activities of ATP:citrate lyase (EC 4.1.3.8), malic enzyme (EC 1.1.1.40) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) at different fermentation stages. According to the analysis, a regulation strategy was proposed which reinforced acetyl-CoA and NADPH supply at a specific fermentation stage. DHA content of total fatty acids was increased from 35 to 60% by the addition of 4 g/L malic acid at the rapid lipid accumulation stage. Total lipid content also showed an apparent increase of 35% and reached 19 g/L when 40 mL ethanol/L was added at the late lipid accumulation stage.     

Immobilization of Cross-Linked Phenylalanine Ammonia Lyase Aggregates in Microporous Silica Gel

A separable and highly-stable enzyme system was developed by adsorption of phenylalanine ammonia lyase (PAL) from Rhodotorula glutinis in amino-functionalized macroporous silica gel and subsequent enzyme crosslinking. This resulted in the formation of cross-linked enzyme aggregates (PAL-CLEAs) into macroporous silica gel (MSG-CLEAs). The effect of adsorptive conditions, type of aggregating agent, its concentration as well as that of cross-linking agent was studied. MSG-CLEAs production was most effective using ammonium sulfate (40%-saturation), followed by cross-linking for 1 h with 1.5% (v/v) glutaraldehyde. The resulting MSG-CLEAs extended the optimal temperature and pH range compared to free PAL and PAL-CLEAs. Moreover, MSG-CLEAs exhibited the excellent stability of the enzyme against various deactivating conditions such as temperature and denaturants, and showed higher storage stability compared to the free PAL and the conventional PAL-CLEAs. Such as, after 6 h incubation at 60°C, the MSG-CLEAs still retained more than 47% of the initial activity whereas PAL-CLEAs only retained 7% of the initial activity. Especially, the MSG-CLEAs exhibited good reusability due to its suitable size and active properties. These results indicated that PAL-CLEAs on MSG might be used as a feasible and efficient solution for improving properties of immobilized enzyme in industrial application.     

Effects of 20 Standard Amino Acids on the Growth,Total Fatty Acids Production,and γ-Linolenic Acid Yield in Mucor circinelloides

Twenty standard amino acids were examined as single nitrogen source on the growth, total fatty acids production, and yield of γ-linolenic acid (GLA) in Mucor circinelloides. Of the amino acids, tyrosine gave the highest biomass and lipid accumulation and thus resulted in a high GLA yield with respective values of 17.8 g/L, 23 % (w/w, dry cell weight, DCW), and 0.81 g/L, which were 36, 25, and 72 % higher than when the fungus was grown with ammonium tartrate. To find out the potential mechanism underlying the increased lipid accumulation of M. circinelloides when grown on tyrosine, the activity of lipogenic enzymes of the fungus during lipid accumulation phase was measured. The enzyme activities of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and ATP-citrate lyase were up-regulated, while NADP-isocitrate dehydrogenase was down-regulated by tyrosine during the lipid accumulation phase of the fungus which suggested that these enzymes may be involved in the increased lipid biosynthesis by tyrosine in this fungus.     

Analysis of factors affecting the performance of partial nitrification in a sequencing batch reactor

The objective of this study was to analyze the factors affecting the performance of partial nitrification in a sequencing batch reactor. During a 140-day long-term operation, influent pH value, dissolved oxygen (DO), and chemical oxygen demand/nitrogen (COD/N) ratio were selected as operating factors to evaluate the maintenance and recovery of nitrite accumulation. Results showed that high DO concentration (2–4 mg/L) could damage nitrite accumulation immediately. However, nitrite accumulation ratio (NAR) could be increased from 1.68?±?1.51 to 35.46?±?7.86 % when increasing the pH values from 7.5 to 8.3 due to the increased free ammonia concentration. Afterwards, stable partial nitrification and high NAR could be recovered when the reactor operated under low DO concentration (0.5–1.0 mg/L). However, it required a long time to recover the partial nitrification of the reactor when the influent COD/N ratios were altered. Fluorescence in situ hybridization analysis implied that ammonium oxidizing bacteria were completely recovered to the dominant nitrifying bacteria in the system. Meanwhile, sludge volumetric index of the reactor gradually decreased from 115.6 to 56.6 mL/g, while the mean diameter of sludge improved from74.57 to 428.8 μm by using the strategy of reducing settling time. The obtained results could provide useful information between the operational conditions and the performance of partial nitrification when treating nitrogen-rich industrial wastewater.     

响应面法优化褐藻胶降解菌Cobetia sp.20发酵培养基

为了提高褐藻胶降解菌株Cobetia sp.20产褐藻胶裂解酶的能力,利用响应面法优化其发酵产褐藻胶裂解酶的培养基。首先利用单因素法分别对发酵培养基中的不同碳源、碳源添加量、不同氮源、氮源添加量以及氯化钠添加量、磷酸二氢钾添加量、硫酸镁添加量和pH进行探究,研究各因素对产酶的影响。在单因素实验的基础上,通过Plackett-Burman试验确定Cobetia sp.20发酵培养基中影响产酶的主要因素。通过响应面试验建立回归方程。研究结果表明,Cobetia sp.20最优发酵培养基配方为褐藻胶15.00 g/L、硫酸铵7.50 g/L、氯化钠15.00 g/L、硫酸镁0.50 g/L、磷酸二氢钾5.30 g/L、硫酸亚铁0.01 g/L、pH值7.58。优化后酶活为142.79 U/mL,比优化前提高了26.36%。褐藻胶裂解酶活的提高,为褐藻胶裂解酶的工业化生产提供了参考。     

Impact of phosphate concentration on docosahexaenoic acid production and related enzyme activities in fermentation of Schizochytrium sp.

Docosahexaenoic acid (DHA) is an important and widely used infant food additive. In this study, the effects of phosphate concentration on lipid and especially DHA synthesis in the oleaginous fungi Schizochytrium sp. HX-308 have been investigated in batch cultures. The maximum DHA yield (8.9 g/L) and DHA productivity (148.3 mg/L h) in 0.1 g/L KH₂PO₄ concentration were higher than the DHA yield (6.2 g/L) and DHA productivity (86.1 mg/L h) in 4 g/L KH₂PO₄ concentration. Furthermore, differences in related enzyme activities (malic enzyme, glucose-6-phosphate dehydrogenase and NAD⁺-isocitrate dehydrogenase) between phosphate-sufficient and phosphate-limitation conditions were assayed. The results showed that the phosphate-limitation condition could maintain higher activities of malic enzyme and glucose-6-phosphate dehydrogenase in addition to lower activity of NAD⁺-isocitrate dehydrogenase. In addition, glucose-6-phosphate dehydrogenase might be the main supplier of NADPH at the early stage of fermentation while malic enzyme might be the provider at the late stage. This information might explain the regulation mechanism of phosphate limitation for lipid production and be useful for further DHA production enhancement.     

Effect of nutritional factors on cellulase enzyme and microbial protein production by Aspergillus terreus and its evaluation

The biomass yield, cellulolytic activity, and protein recovery using Aspergillus terreus GN1 with alkali-treated sugarcane bagasse was studied using different levels (250-600 mg of N/L of broth) of organic and inorganic nitrogen sources. e.g., cattle urine, urea, cornsteep liquor, ammonium sulfate, ammonium nitrate, ammonium iron sulfate, ammonium chloride, and sodium nitrate. Among different levels of alkali-treated bagasse substrate concentrations (0.5-4.0% w/v) tested, 1.0% substrate yielded the highest crude protein content, protein recovery, and cellulolytic activity. The biomass recovery with 1.0% substrate ranged from 290-380 mg/500 mg bagasse substrate in a 50-mL broth with a nitrogen level of 250-600 mg of N/L in all the sources except ammonium iron sulfate, which yielded 402-439 mg/500 mg bagasse substrate. However, crude protein content of biomass obtained with an ammonium iron sulfate nitrogen source was the lowest. Cornsteep liquor nitrogen source at the rate of 600 mg of N/L yielded the maximum crude protein of 32.9%, protein recovery of 22.2 g/100 g of bagasse, and carboxymethyl cellulase and filter paper enzyme activities of 1.1 and 0.09 units/mL, among the organic and inorganic nitrogen sources studied. In general, the organic nitrogen sources and inorganic nonammonium nitrogen sources were utilized preferentially for protein production over the inorganic ammonium nitrogen sources. The fermentation time required under optimum cultural and nutritional conditions for A. terreus GN1 was also evaluated. The crude protein content of the biomass increased gradually up to the seventh day of fermentation, but the protein recovery rate was high up to two or three days. It was observed that the cellulose utilization rate increased after an initial lag of one day up to the third day and gradually increased further, which corresponded positively with protein content, biomass protein recovery, and cellulase enzyme activity. On the seventh day of fermentation, the crude protein content, biomass protein recovery, water-soluble carbohydrate, bagasse cellulose utilization, CMCase, and FPase activities were 32.8%, 20.1 g/100 g of bagasse, 6.2%, 82.7%, 1.0. and 0.08 U/mL, respectively. The final biomass recovered contained 32.8% crude protein content and had an in vitro rumen digestibility (IVRD) coefficient of 68.8%. The biomass contained almost all the essential and nonessential amino acids and was comparable with FAO reference protein. It is concluded that a fermentation time of 72 h gave a faster rate of protein production of 16.9 g/100 g of bagasse with 69.8% bagasse cellulose utilization with 76.0% IVRD. and contained almost all the essential and nonessential amino acids.     

The effect of pH on the efficiency of an SBR processing piggery wastewater

To treat piggery wastewater efficiently, the hydrolysis of urea (mainly derived from swine urine) in piggery wastewater with the change of sewage pH must be considered. Using activated sludge, piggery wastewater was treated in a sequencing batch reactor (SBR), and the effects of influent pH on SBR processing efficiency, sludge settle ability, and sludge activity were investigated. The results showed that a high influent pH value contributed to the improvement of the removal rate of ammonia nitrogen and reduction of the chemical oxygen demand (COD). When the influent pH was between 9.0 and 9.5, the removal rate of ammonia nitrogen was higher than 90%, and the reduction of COD from its original value was 80%. The influent pH had a greater influence on sludge concentration and sludge activity. When the influent pH increased from 7.0 to 9.5, the sludge concentration increased from 2,350 to 3,947 mg/L in the reactor, and the activities of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) first increased and then decreased. When the influent pH was 9.0 and 8.0, the maximum values (0.48 g O₂/(g MLSS/day) and 0.080 g O₂/(g MLSS/day)) were reached, and the sludge settling ratio was nearly steady between 20 and 35% in each reactor.     

Ammonium removal using algae–bacteria consortia: the effect of ammonium concentration,algae biomass,and light

In this study, the effects of ammonium nitrogen concentration, algae biomass concentration, and light conditions (wavelength and intensity) on the ammonium removal efficiency of algae-bacteria consortia from wastewater were investigated. The results indicated that ammonium concentration and light intensity had a significant impact on nitrification. It was found that the highest ammonia concentration (430 mg N/L) in the influent resulted in the highest ammonia removal rate of 108 ± 3.6 mg N/L/days, which was two times higher than the influent with low ammonia concentration (40 mg N/L). At the lowest light intensity of 1000 Lux, algae biomass concentration, light wavelength, and light cycle did not show a significant effect on the performance of algal–bacterial consortium. Furthermore, the ammonia removal rate was approximately 83 ± 1.0 mg N/L/days, which was up to 40% faster than at the light intensity of 2500 Lux. It was concluded that the algae-bacteria consortia can effectively remove nitrogen from wastewater and the removal performance can be stabilized and enhanced using the low light intensity of 1000 Lux that is also a cost-effective strategy.     

城市生活废水用于产油微藻培养

将废水与产油微藻培养结合起来,可以实现废水的无害化处理,还可为微藻的培养提供营养组分和大量水源。利用高产油栅藻,以城市生活废水为水源,在气泡柱式光反应器中,考察了添加不同营养组分对栅藻细胞的生长、生物质产量、总脂含量以及氮磷的去除情况的影响。结果表明：生活废水非常适合于产油微藻的培养,利用生活废水进行微藻培养中,仅需补充添加无机氮、无机磷、柠檬酸铁铵以及微量元素。但这些营养组分的加入量对藻细胞的生长、生物量和油脂积累有重要影响。在优化的废水培养基中微藻细胞浓度可达8.0 g/L左右,远高于标准BG11培养基5.0 g/L的水平。微藻细胞对于无机氮与磷有着高的吸收能力,在废水中加入185.25 mg/L以下无机氮,16.1 mg/L以下无机磷的条件下培养3~4 d后,培养液水体中未检测到有氮磷残留。由此表明利用城市生活废水培养含油微藻可以在获得微藻油脂产品的同时实现水体的无害化处理。     

产丁二酸工程菌的构建及其厌氧发酵

为了考察过量表达苹果酸酶对于E.coli NZN111(ldhA::Kan pfl::Cam)厌氧发酵产丁二酸的影响, 将连接有苹果酸酶基因sfcA的表达载体pTrc99a-sfcA转化进NZN111中, 构建了重组NZN111(pTrc99a-sfcA)。0.5 mmol/L IPTG诱导8 h后, 测定的苹果酸酶比酶活为30.67 u/mg, 比受体菌提高了140倍。采用两阶段发酵模式, 结果表明: 过量表达的苹果酸酶在NZN111体内催化了从丙酮酸到苹果酸的逆向反应, 丁二酸是发酵过程中积累的主要有机酸, 且当加入0.7 mmol/L IPTG诱导, 初始葡萄糖糖浓度为18.5 g/L时, 选择对数生长期后期的菌种以10%的接种量转入厌氧发酵, 发酵结束时发酵液中丁二酸的浓度为12.84 g/L, 对葡萄糖的收率为69.43%, 乙酸为0.58 g/L, 二者浓度比为22:1, 没有检测到甲酸和乳酸。构建的菌种具有高产丁二酸和副产物极少的优点, 在同类菌种中处于先进水平。     

磷酸氢二铵对糙皮侧耳菌丝生长及基质降解酶活性的影响

氮源种类和浓度均会对糙皮侧耳Pleurotus ostreatus菌丝长势、生长速率以及代谢产生影响,而氮匮乏与氮过量积累都会对糙皮侧耳的生长产生不利影响。为了研究氮源对糙皮侧耳菌丝生长和基质降解酶活性的影响,本研究选取磷酸氢二铵[(NH4)2HPO4]作为唯一氮源,通过在培养基中添加不同浓度的磷酸氢二铵检测糙皮侧耳菌丝生长速率和木质纤维素降解酶的活性,筛选出糙皮侧耳生长的最适磷酸氢二铵浓度。结果表明,当磷酸氢二铵的添加浓度区间为10–20 mmol/L时菌丝长势最好。以缺氮时的酶活作为对照,当磷酸氢二铵的添加浓度为10 mmol/L时,羧甲基纤维素酶的活力最强,显著高于对照组(P<0.05);当添加浓度为5 mmol/L时,滤纸纤维素酶的活力最强,显著高于对照组(P<0.05),而10 mmol/L浓度下的酶活力比5 mmol/L时稍有下降,但二者之间无显著性差异(P>0.05);当添加浓度为40 mmol/L时,木聚糖酶的活力最强,显著高于对照组(P<0.05);当添加浓度为10mmol/L时,漆酶的活力最强,显著高于对照组(P<0.05)。基质降解酶...     

Influence of ammonium and extracellular pH on the amino and organic acid contents of suspension culture cells of Acer pseudoplatanus

The effects of supplied ammonium and nitrate on the amino and organic acid contents and enzyme activities of cell suspension cultures of Acer pseudoplatanus L. were examined. Regardless of nitrogen source the pH of the culture medium strongly affected the malate and citrate contents of the cells; these organic acid pools declined at pH 5, but increased at pH 7 and 8. Over a period of two days, ammonium had little effect on the responses of the organic acid pool sizes to the pH of the medium. In contrast, ammonium had a strong influence on amino acid pool sizes, and this effect was dependent on the pH of the medium. At pH 5 there was no increase in cell ammonium or amino acid contents, but at higher pH values cellular ammonium content rose, accompanied by accumulation of glutamine, glutamate and asparagine. Over several days, supplied ammonium led to an increase in activity of glutamate dehydrogenase irrespective of any changes in internal ammonium and amino acid contents. If the pH of the medium was allowed to fall below pH 4 in the presence of ammonium, phosphoenolpyruvate (PEP) carboxylase activity declined to a very low value over several days; at higher pH, the activity of this enzyme, and that of NAD malic enzyme and NAD malate dehydrogenase, remained substantial irrespective of whether the nitrogen source was NH⁺₄ or NO-₃.     

氨氮对中华小长臂虾的急性毒性及非特异性免疫指标的影响

采用生物毒性实验方法研究了氨氮对中华小长臂虾的急性毒性作用, 结果表明: 在温度为(18±1)℃, pH为7.3±0.1条件下, 氨氮对中华小长臂虾24h、48h、72h、96h 的半致死浓度(LC₅₀)分别为565.47、371.16、291.16和272.50 mg/L, 安全浓度为 27.25 mg/L。转化为非离子氨的LC₅₀分别为3.74、2.45、1.93 和1.80 mg/L, 安全浓度为0.18 mg/L。根据96h 的LC₅₀和安全浓度按照等差数列设置5个氨氮浓度梯度, 分别60、100、140、180和220 mg/L, 研究氨氮胁迫对中华小长臂虾非特异性免疫指标的影响。结果显示: 在24h时, 除了220 mg/L的肌肉组织, 中华小长臂虾肝胰腺和肌肉中的超氧化物歧化酶(SOD)活性显著性高于对照组, 并具有明显的剂量效应, 在48—96h均回落到正常水平; 在24h时, 中华小长臂虾氨氮处理组中肝胰腺的酸性磷酸酶(ACP)与对照组未发生显著变化, 而碱性磷酸酶(AKP)则显著高于对照组, 在48—96h两者的140、180和220 mg/L处理组均显著低于对照组; 除了140 mg/L 处理组的ACP活性外, 肌肉中的ACP和AKP活性从24h开始就出现了显著性下降, 始终低于对照组。研究获得了氨氮对中华小长臂虾的急性毒性结果和在高氨氮胁迫下非特异性免疫指标的变化规律, 发现中华小长臂虾对氨氮具有较强的耐受性, 但高浓度的氨氮会对中华小长臂虾的免疫酶活性产生抑制作用, 研究结果可为中华小长臂虾健康养殖发展提供科学依据。     

不同培养模式下魏氏真眼点藻生长和产油特性的研究

为了解魏氏真眼点藻(Eustigmatos vischeri Hibberd)的生物学特性,探究"批量法"、"两步法"、"补料法"和"添加碳酸氢盐"4种不同培养模式对魏氏真眼点藻生长和油脂积累的影响,本文分别采用不同初始浓度的硝酸钠供应、更换培养基、分次少量补加硝酸钠及添加低浓度Na HCO3或NH4HCO3等方法培养魏氏真眼点藻。结果显示,"批量"培养下,硝酸钠浓度为3.0 mmol/L时藻细胞生物量达到8.41 g/L,油脂最高可达到65.16%,油脂产率为0.30 g·L-1·d-1。"两步法"和"补料法"培养对藻细胞油脂积累没有显著影响,而通过"添加碳酸氢盐"培养对该藻细胞生长和油脂积累的效果最显著,其中Na NO3+NH4HCO3组生物量达到11.56 g/L,油脂最高达60.92%,与相同氮浓度"批量"培养相比,生物质浓度提高了1.0 g/L,总脂含量提高了10%,大大提高了该藻的总脂产率(达到0.39 g·L-1·d-1)。因此,魏氏真眼点藻是一株高产油藻株,当添加低浓度碳酸氢铵时最有利于促进该藻生物质浓度和总脂含量的提高,这是一种最佳的培养模式,具有潜在的开发和利用价值。     

Optimization of free ammonia concentration for nitrite accumulation in shortcut biological nitrogen removal process

A shortcut biological nitrogen removal (SBNR) utilizes the concept of a direct conversion of ammonium to nitrite and then to nitrogen gas. A successful SBNR requires accumulation of nitrite in the system and inhibition of the activity of nitrite oxidizers. A high concentration of free ammonia (FA) inhibits nitrite oxidizers, but unfortunately decreases the ammonium removal rate as well. Therefore, the optimal range of FA concentration is necessary not only to stabilize nitrite accumulation but also to achieve maximum ammonium removal. In order to derive such optimal FA concentrations, the specific substrate utilization rates of ammonium and nitrite oxidizers were measured. The optimal FA concentration range appeared to be 5–10 mg/L for the adapted sludge. The simulated results from the modified inhibition model expressed by FA and ammonium/nitrite concentrations were shown very similar to the experimental results.