无机碳源对小球藻自养产油脂的影响

旨在研究小球藻利用无机碳自养产油脂,考察了3种无机碳源 (Na2CO3、NaHCO3和CO2) 及其初始浓度对小球藻产油特性的影响。结果表明,小球藻能利用Na2CO3、NaHCO3和CO2产油;经Na2CO3、NaHCO3和CO2培养10 d后,随着每种无机碳源浓度的增加,小球藻产量均先增加后减少。小球藻经3种无机碳源培养后,其培养液pH值上升。最适宜的Na2CO3和NaHCO3添加量均为40 mmol/L,其生物量分别达到0.52 g/L和0.67 g/L,产油量分别达到0.19 g/L和0.22 g/L。在3种无机碳源中,CO2是最佳无机碳源,当CO2浓度为6％时,小球藻生长最快,生物量达2.42 g/L,产油量最高达0.72 g/L;当CO2浓度过低时,无机碳供应不足,油脂产量低;当CO2浓度过高时,培养液pH偏低,小球藻油脂积累受到抑制。Na2CO3和NaHCO3较CO2更有利于小球藻积累不饱和脂肪酸。     

Concomitant wastewater treatment with lipid and carotenoid production by the oleaginous yeast Rhodosporidium toruloides grown on brewery effluent enriched with sugarcane molasses and urea

In this study, secondary brewery wastewater (SBWW) supplemented with sugarcane molasses (SCM) was used for SBWW treatment with concomitant lipid and carotenoid production by the yeast Rhodosporidium toruloides NCYC 921. In order to improve the biomass production, ammonium sulfate, yeast extract and urea were tested as nitrogen sources. Urea was chosen as the best low-cost nitrogen source. A fed-batch cultivation was carried out with SBWW supplemented with 10 g L⁻¹ of sugarcane molasses as carbon source, and 2 g L⁻¹ of urea as nitrogen source. A maximum biomass concentration of 42.5 g L⁻¹ was obtained at t = 126.5 h and the maximum biomass productivity was 0.55 g L⁻¹ h⁻¹ at t = 48.25 h. The maximum lipid content was 29.9 % w/w (DCW) at t = 94 h of cultivation and the maximum carotenoid content was 0.23 mg g⁻¹ at 120 h of cultivation. Relatively to the SBWW treatment, after the batch phase, 45.8 % of total Kjeldahl nitrogen removal, 81.7 % of COD removal and 100 % of sugar consumption were observed. Flow cytometry analysis revealed that 27.27 % of the cells had injured membrane after the inoculation. This proportion was reduced to 10.37 % at the end of the cultivation, indicating that cells adapted to the growth conditions.     

Influence of growth conditions on the production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi

The influence of growth parameters on the fermentative production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi was studied. The bacteriocin production was greatly affected by carbon and nitrogen sources. Strain A164 produced at least 4-fold greater bacteriocin in M17 broth supplemented with lactose than other carbon sources. The amount of 3% yeast extract was found to be the optimal organic nitrogen source. While the maximum biomass was obtained at 37 degrees C, the optimal temperature for the bacteriocin production was 30 degrees C. The bacteriocin production was also affected by pH of the culture broth. The optimal pH for growth and bacteriocin production was 6.0. Although the cell growth at pH 6.0 was nearly the same level at pH 5.5 and 6.5, the greater bacteriocin activity was observed at pH 6.0. Exponential growth took place only during an initial period of the cultivation, and then linear growth was observed. Linear growth rates increased from 0.160 g(DCW) x l(-1) x h(-1) to 0.245 g(DCW) x l(-1) x h(-1) with increases in lactose concentrations from 0.5 to 3.0%. Maximum biomass was also increased from 1.88 g(DCW) x l(-1) to 4.29 g(DCW) x l(-1). However, increase in lactose concentration did not prolong the active growth phase. After 20 h cultivation, cell growth stopped regardless of lactose concentration. Production of the bacteriocin showed primary metabolic kinetics. However, bacteriocin yield based on cell mass increased greatly during the late growth phase. A maximum activity of 131x10(3) AU x ml(-1) was obtained at early stationary growth phase (20 h) during the batch fermentation in M17L broth (3.0% lactose) at 30 degrees C and pH 6.0.     

Optimization of culture conditions and comparison of biomass productivity of three green algae

Culture conditions for the mass production of three green algae, Chlorella sp., Dunaliella salina DCCBC2 and Dunaliella sp., were optimized using a response surface methodology (RSM). A central composite design was applied to investigate the effects of initial pH, nitrogen and phosphate concentrations on the cultivation of microalgae. The optimal growth conditions estimated from the design are as follows: Chlorella sp. (initial pH 7.2, ammonium 17 mM, phosphate 1.2 mM), D. salina DCCBC2 (initial pH 8.0, nitrate 3.3 mM, phosphate 0.0375 mM) and Dunaliella sp. (initial pH 8.0, nitrate 3.7 mM, phosphate 0.17 mM). Culturing the microalgae with the optimized conditions confirmed that the maximum growth rates were attained for these parameters. The optimum CO(2) concentrations of Chlorella sp., D. salina DCCBC2 and Dunaliella sp. were 1.0, 3.0 and 1.0% (v/v), respectively. The specific growth rates (μ) of Chlorella sp., D. salina DCCBC2 and Dunaliella sp. were 0.58, 0.78 and 0.56 day(-1), respectively, and the biomass productivities were 0.28, 0.54 and 0.30 g dry cell wt l(-1) day(-1), respectively. The CO(2) fixation rates of Chlorella sp., D. salina DCCBC2 and Dunaliella sp. were 42.8, 90.9 and 45.5 mg l(-1) day(-1), respectively. Mixotrophic cultivation of Chlorella sp. with glucose increased biomass productivity from 0.28 to 0.51 g dry cell wt l(-1) day(-1). However, D. salina DCCBC2 and Dunaliella sp. were not stimulated by several organic compounds tested.     

Effect of light supply and carbon source on cell growth and cellular composition of a newly isolated microalga Chlorella vulgaris ESP‐31

Light supply is one of the most important factors affecting autotrophic growth of microalgae. This study investigated the effect of the type and light intensity of artificial light sources on the cell growth of an indigenous microalga Chlorella vulgaris ESP‐31 obtained from southern Taiwan. In addition, a dissolved inorganic carbon source (i.e. sodium bicarbonate) was used to improve the biomass production of strain ESP‐31. The results show that a new fluorescent light source (TL5) was effective in indoor cultivation of microalgae. Better overall productivity of 0.029 g dry cell weight/L‐d was obtained when using TL5 lamps as the light source with a light intensity of 9 W/m². A carbon source (sodium bicarbonate) concentration of 1000 mg/L was found to be optimal for the growth of strain ESP‐31 in terms of both biomass production and carbon source utilization. Under the optimal growth conditions, the resulting microalgal biomass consisted of 25–30% protein, 6–10% carbohydrate, and 30–40% lipid.     

Assessment of <Emphasis Type="Italic">Nannochloropsis gaditana</Emphasis> growth and lipid accumulation with increased inorganic carbon delivery

Algal biomass refineries for sustainable transportation fuels, in particular biodiesel, will benefit from algal strain enhancements to improve biomass and lipid productivity. Specifically, the supply of inorganic carbon to microalgal cultures represents an area of great interest due to the potential for improved growth of microalgae and the possibility for incorporation with CO₂ mitigation processes. Combinations of bicarbonate (HCO₃^?) salt addition and application of CO₂ to control pH have shown compelling increases in growth rate and lipid productivity of fresh water algae. Here, focus was placed on the marine organism, Nannochloropsis gaditana, to investigate growth and lipid accumulation under various strategies of enhanced inorganic carbon supply. Three gas application strategies were investigated: continuous sparging of atmospheric air, continuous sparging of 5% CO₂ during light hours until nitrogen depletion, and continuous sparging of atmospheric air supplemented with 5% CO₂ for pH control between 8.0 and 8.3. These gas sparging schemes were combined with addition of low concentrations (5 mM) of sodium bicarbonate at inoculation and high concentration (50 mM) of sodium bicarbonate amendments just prior to nitrogen depletion. The optimum scenario observed for growth of N. gaditana under these inorganic carbon conditions was controlling pH with 5% CO₂ on demand, which increased both growth rate and lipid accumulation. Fatty acid methyl esters were primarily comprised of C16:0 (palmitic) and C16:1 (palmitoleic) aliphatic chains. Additionally, the use of high concentration (50 mM) of bicarbonate amendments further improved lipid content (up to 48.6%) under nitrogen deplete conditions when paired with pH-controlled strategies.     

Lipid production by microalgae <Emphasis Type="Italic">Chlorella protothecoides</Emphasis> with volatile fatty acids (VFAs) as carbon sources in heterotrophic cultivation and its economic assessment

Volatile fatty acids (VFAs) that can be derived from food wastes were used for microbial lipid production by Chlorella protothecoides in heterotrophic cultures. The usage of VFAs as carbon sources for lipid accumulation was investigated in batch cultures. Culture medium, culture temperature, and nitrogen sources were explored for lipid production in the heterotrophic cultivation. The concentration and the ratio of VFAs exhibited significant influence on cell growth and lipid accumulation. The highest lipid yield coefficient and lipid content of C. protothecoides grown on VFAs were 0.187 g/g and 48.7 %, respectively. The lipid content and fatty acids produced using VFAs as carbon sources were similar to those seen on growth and production using glucose. The techno-economic analysis indicates that the biodiesel derived from the lipids produced by heterotrophic C. protothecoides with VFAs as carbon sources is very promising and competitive with other biofuels and fossil fuels.     

碳源种类及碳氮比对眼点拟微绿球藻生长密度、油脂含量和脂肪酸组成的影响

研究了三种碳源Na2CO3、NaHCO3、葡萄糖对眼点拟微绿球藻生长密度和油旨含量的影响,实验结果表明相对于葡萄糖,无机碳源NaHCO3更利于眼点拟微绿球藻的生长.以NaHCO3为碳源,研究了在不同的接种密度、NaNO3浓度下,C/N对眼点拟微绿球藻生长密度和油脂含量的影响.实验结果表明,C/N对眼点拟微绿球藻生长密度的影响与接种密度和NaNO3浓度有关,在高的NaNO3浓度时,C/N对眼点拟微绿球藻生长密度的影响很小;在低的NaNO3浓度时,随着C/N比的增加,微绿球藻的生长密度先增加后下降,存在最佳的C/N比.最佳的C/N比随接种密度而变化,在接种密度为OD440=0.10时,最佳C/N比为3,当接种密度提高到OD440=0.70时,最佳C/N比增加到5.NaNO3浓度和C/N对微藻油脂含量均有较大影响,在不同的接种密度和NaNO3浓度下都表现为C/N=1时最利于微藻油脂的积累,这与卡尔文循环过程中核酮糖-1,5-二磷酸羧化酶/加氧酶的活性有关.本实验的最佳产油培养条件为以NaHCO3为碳源,初始接种密度为OD440=0.70,C/N=1∶1,CNaNO3=0.225g/L,此时油脂产率为56.7 mg/(L·d),EPA产率为6.5 mg/(L·d).     

产油微藻的分离、筛选及自养培养氮源、碳源的优化

从云南滇池的水样中分离筛选得到一株自养产油小球藻(Chlorella vulgaris,C.vulgaris),其油脂产率可达28.6mg/(L·d),进一步考察了不同氮源、氮源浓度和添加无机碳源对其自养生长和油脂积累的影响。结果表明,硝酸钠为优化氮源,氮元素的优化浓度为123mg/L,油脂含量随氮元素浓度升高而降低;添加NaHCO3显著提高了C.vulgaris生物量产率和油脂产率,其优化浓度为800mg/L。在氮源和碳源的优化浓度下,C.vulgaris的最大生物量产率和油脂产率可达332.8mg/(L·d)和100.2mg/(L·d),分别是对照组的3.6和3.4倍。     

Influence of cultivation conditions on lipid production by Cryptococcus albidus

Summary Cryptococcus albidus var. albidus CBS 4517 was able to accumulate lipid under nitrogen-limited as well as excess-nitrogen conditions. The highest lipid-producting capacity was, however, observed in nitrogen-limited cultivations. In nitrogen-limited batch cultures, a lipid content of 34% (w/w) in biomass and a maximum specific lipid productivity of 37 mg lipid/g lipid-free biomass·h, was determined. The yield of lipid from glucose was about 0.15 g/g in nitrogen-limited and 0.11 g/g in excess-nitrogen cultures.In a nitrogen-limited fed-batch culture, 12.4 g/l lipid was produced at 90 h of cultivation and the cells contained 46.3% (w/w) lipid.Higher lipid yield and cellular lipid content were observed when inorganic nitrogen sources were used compared with organic. The choice of carbon source was seen to influence growth as well as lipid production and the highest yields of lipid were obtained when glucose, maltose or mannitol was used.A cultivation temperature of 20°C provided the highest lipid productivity compared to 25°C and 30°C. Addition of citrate to the growth medium was seen to have a stimulating effect on the specific lipid productivity.     

一株重金属镉耐受小球藻的分离鉴定及其生长条件优化

以龙江河镉污染水体预留样本为实验材料,从中筛选得到一株重金属镉耐受藻株,经形态和分子生物学鉴定为小球藻属,命名为Chlorella sp.LQQ-1。实验从温度、pH、Cd²⁺、有机碳源及有机氮源等方面对该藻株生长条件进行优化,并考察其在最佳生长条件下对水体中Cd²⁺的去除效果。结果表明:该小球藻最适宜生长温度为30℃,最适宜pH为7.0左右。Cd²⁺在低浓度下能促进小球藻的生长,当Cd²⁺浓度超过30μmol·L^-1时,小球藻的生长受到抑制。适宜该小球藻生长的最佳葡萄糖添加浓度为10g·L^-1,最佳尿素添加浓度为1g·L^-1。在最佳生长条件下,该小球藻对水体中Cd²⁺的去除率达89.7%。     

Physiological conditions for nitrogen fixation in a unicellular marine cyanobacterium, Synechococcus sp. strain SF1.

A marine, unicellular, nitrogen-fixing cyanobacterium was isolated from the blades of a brown alga, Sargassum fluitans. This unicellular cyanobacterium, identified as Synechococcus sp. strain SF1, is capable of photoautotrophic growth with bicarbonate as the sole carbon source and dinitrogen as the sole nitrogen source. Among the organic carbon compounds tested, glucose and sucrose supported growth. Of the nitrogen compounds tested, with bicarbonate serving as the carbon source, both ammonia and nitrate produced the highest growth rates. Most amino acids failed to support growth when present as sole sources of nitrogen. Nitrogenase activity in Synechococcus sp. strain SF1 was induced after depletion of ammonia from the medium. This activity required the photosynthetic utilization of bicarbonate, but pyruvate and hydrogen gas were also effective sources of reductant for nitrogenase activity. Glucose, fructose, and sucrose also supported nitrogenase activity but to a lesser extent. Optimum light intensity for nitrogenase activity was found to be 70 microE/m2 per s, while the optimum oxygen concentration in the gas phase for nitrogenase activity was about 1%. A hydrogenase activity was coinduced with nitrogenase activity. It is proposed that this light- and oxygen-insensitive hydrogenase functions in recycling the hydrogen produced by nitrogenase under microaerobic conditions.     

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。     

Heterotrophic growth and nutritional aspects of the diatom Cyclotella cryptica (Bacillariophyceae): effect of nitrogen source and concentration

To investigate the nutritional value of the diatom Cyclotella cryptica Reimann, Lewin, and Guillard as an alternative feed for the use in the aquaculture industry, the heterotrophic growth characteristics, total fatty acids, and the resultant fatty acid profile of the microalga were studied when cultivated with sodium nitrate, ammonium chloride, or urea. All three nitrogen sources supported growth under heterotrophic conditions, and their uptake affected the pH of the cultivation medium, even when buffered. The use of sodium nitrate or urea resulted in a significant increase in the pH of the cultivation media, whereas the use of ammonium chloride caused a minor decrease in the pH of the cultivation media. The maximum specific growth rate was highest when urea and ammonium chloride were supplied at a low concentration; however, the total fatty acid content was not significantly affected (P = 0.101) by the nitrogen source when supplied at 10.7 mM nitrogen. The total fatty acid content and fatty acid profile of C. cryptica was more affected by the growth phase (predominately influenced by the initial nitrogen concentration) than by the source of nitrogen.     

碳源、氮源对异养单针藻Monoraphidium sp. FXY-10油脂积累和脂肪酸组成的影响

研究了碳源与氮源对单针藻Monoraphidium sp. FXY-10异养培养的影响。以BG-11为基础培养基,通过添加不同类型、浓度梯度碳源和氮源,比较分析微藻生物量、油脂积累以及脂肪酸组成。结果表明,以葡萄糖作碳源,硝酸钠为氮源,微藻细胞积累的油脂是理想的生物柴油制备原料。硝酸钠浓度分别为1.00、3.00和5.00 g/L时,对油脂产量影响不显著(P>0.05)。葡萄糖浓度为10.00 g/L,硝酸钠为氮源油脂产量达到实验最高值0.84 g/L,其油脂脂肪酸组成主要由C16:0和C18:1等短链饱和脂肪酸和单不饱和脂肪酸组成,不饱和度值(DU)为61.98,相对偏低。     

小球藻联产油脂和虾青素的基元模式分析

构建了包含虾青素合成途径的小球藻代谢网络模型,集成文献报道同位素标定的小球藻代谢通量数据,估算了胞内代谢通量分布。在正常和缺氮培养条件下,虾青素的代谢通量分别为0.38和0.35。计算得到基元模式共640条,通过最大熵原理算法求取了正常培养和缺氮培养条件下的基元模式概率。存在4条关键基元模式,在2种培养条件下,其基元模式概率之和分别为60.95%和77.53%。虾青素的最大理论合成产率为11.27%,但是这4条关键基元模式并不包括虾青素的合成反应。     

Lipid accumulation in an oleaginous yeast (Candida 107) growing on glucose in single-stage continuous culture.

Lipid accumulation of Candida 107, grown at dilution rates from 0.03 to the maximum of 0.21/h, with carbon, nitrogen, phosphate, and magnesium limitations in a chemostat, was maximal at about 40% (wt/wt) with nitrogen-limited medium at a dilution rate of 0.06/h, giving an efficiency of substrate conversion of 22 g of lipid per g of glucose consumed. At higher dilution rates the lipid content decreased. With carbon-limited growth, the highest lipid content (14%, wt/wt) was at the maximum dilution rate. High lipid contents also occurred with phosphate + nitrogen as double limitations of growth, with the lipid content of the yeast (about 35%, wt/wt) continuing to be near maximum at dilution rates also near maximum (0.17/h), thus giving the highest specific rate of lipid formation of any growth conditions (0.59 g of lipid/g of yeast per h). However, the efficiency of substrate utilization was only 5.2 g of lipid formed per 100 g of glucose consumed. The composition of the fatty acyl residues within the lipid remained constant over many weeks if the steady-state conditions remained unchanged. With carbon-limited growth, the degree of unsaturation of the fatty acids markedly decreased as the dilution rate was increased, but with nitrogen limitation the reverse trend was seen. In all cases, linoleic and oleic acids were the principal fatty acyl residues affected, and their relative proportions always varied in opposite directions. When magnesium was a limiting nutrient, there was a considerable increase in the proportion of myristic acid produced within the lipid. Neutral lipids (predominantly triglycerides) varied from 66 to 92% of the total lipid from carbon- and nitrogen-limited growth; phospholipids (varying from 2 to 25%) were highest in nitrogen-limited growth. The fatty acyl residues within each lipid fraction showed the same variations with changing growth rates.     

Poly-3-hydroxybutyrate production byAzotobacter chroococcum

Thirty-seven soil isolates and mutants ofAzotobacter chroococcum tested for poly-3-hydroxybutyrate (PHB) production using Sudan black B staining method were found to be positive. One mutant showed a higher number of PHB-producing cells and maximum number of granules per cell. Using 2% glucose and 15 mmol/L ammonium acetate, PHB production was found to be maximum at 36 and 48 h of growth under submerged cultivation and under stationary cultivation, respectively. PHB production was found to be higher on sucrose and commercial sugar (as carbon sources) as compared to glucose and mannitol. As commercial sugar is cheaper than sucrose it was selected as carbon source for PHB production, that being found to be maximum at 1% concentration. Inorganic nitrogen sources seemed to have no stimulatory effect on the production of PHB. However, ammonium acetate (15 mmol/L) was found to be best for PHB production. Peptone (0.2 %) gave a better yield of PHB under both growth conditions. Using all optimized conditions, PHB production was studied in ten selected strains. Two of them were found to be best PHB producers under both growth conditions, one producing 621 and 740 μg/g dry mass under submerged cultivation and under stationary cultivation, respectively, while the second one produced 589 and 733 μg/g.     

不同碳源对小球藻Chlorella zofingiensis异养产虾青素的影响

研究了葡萄糖、蔗糖和果糖对小球藻(Chlorella zofingiensis)异养生长及产虾青素的影响,结果表明,在糖浓度为20g/L时,细胞生长较快,但干重较小,虾青素含量较低;在糖浓度为50g/L时,细胞生长较慢,但干重较大,虾青素含量较高。3种碳源中蔗糖和葡萄糖效果较好,在蔗糖浓度为50g/L时,虾青素含量和产量分别达到0.94mg/g和9.61mg/L。