异养小球藻产总脂肪酸的培养基优化

研究了异养小球藻(Chlorella protothecoides)分批培养基中葡萄糖和硝酸盐浓度对生物量、总脂和总脂肪酸产量的影响.结果表明,当细胞在含有40 g·L-1葡萄糖和0.1 mol·L-1 NaNO3的异养培养基中生长时,总脂和总脂肪酸的产量可分别达到最高值为3.83 g·L-1和1.64 g·L-1,同时C18脂肪酸占总脂肪酸的比例超过69%,总脂肪酸占总脂的比例也高达42.63%,总脂含量约为24.3%.通过优化异养小球藻培养基中的葡萄糖和硝酸盐浓度,能够获得高产总脂肪酸,进而生产生物柴油.     

培养基营养调控对小球藻Chlorella protothecoides胞内生化成分积累的影响

目的研究调控异养培养基中碳源和氮源浓度对小球藻Chlorella protothecoides(C.protothecoides)胞内生化成分积累的影响。方法分别以葡萄糖为碳源(尿素初始浓度为3 g/L,葡萄糖浓度分别为10、20、30、40、50 g/L)、尿素为氮源(葡萄糖初始浓度为30 g/L,尿素浓度分别为3.00、0.00、0.15、0.30、0.45、0.60 g/L),避光培养小球藻细胞,收集藻液,制备冻干藻粉。采用傅里叶变换红外光谱法(Fourier transform infrared spectroscgy,FTIR)测定小球藻胞内蛋白质、油脂和碳水化合物的变化。结果当培养基葡萄糖浓度为30 g/L,尿素浓度为3 g/L时,蛋白质吸收峰强度最大,相对含量较高,碳水化合物次之,油脂含量最低;与氮充足(3.00 g/L)条件下相比,氮缺失(0.00 g/L)条件下,蛋白质吸收峰强度骤然降低43.22%,油脂增高1.41倍,碳水化合物提高6.04%。结论培养基中不同碳、氮水平可实现胞内不同大分子组分(油脂、蛋白质和碳水化合物)产量的调控,满足不同层次的工业需求。     

有机碳源对异养小球藻生长、蛋白质和叶绿素含量的影响

研究了分别以葡萄糖、蔗糖和乙酸钠为唯一有机碳源异养养殖小球藻的生长、蛋白质和叶绿素合成。葡萄糖和乙酸钠培养的小球藻都出现了高浓度抑制生长的现象,小球藻在葡萄糖和乙酸钠中的最适生长浓度分别为25 g/L和35g/L,最大OD_(680)为5.45和1.93。但是小球藻的生物量随蔗糖浓度增大而增大,当蔗糖浓度为45g/L时出现了最大OD6_(80) 8.13。乙酸钠、蔗糖、葡萄糖培养42小时的小球藻的蛋白质含量分别为18%、15 %和14%,叶绿素含量分别为:17、10、8 mg/g。综合考虑小球藻生长、蛋白质及叶绿素合成,25 g/L葡萄糖是小球藻异养的最适有机碳源。     

大规模异养发酵培养小球藻USTB-01研究

采用异养小球藻USTB-01,分别在50、500 L和5 000 L发酵罐逐级放大进行异养发酵培养的优化控制研究.结果表明,随着小球藻异养培养过程中生物量的增大,按照3个不同阶段逐渐加大葡萄糖和硝酸钾(C/N质量比为20:1)分别作为碳源和氮源的流加量.可以大幅度提高小球藻USTB-O1的生长速度.72 h内,分别在50、500 L和5 000 L发酵罐进行异养发酵培养小球藻USTB-01过程中,都获得了质量浓度40 g/L以上的藻细胞干重,在培养物中保持低浓度的葡萄糖和硝酸钾在支持小球藻快速生长方面发挥了重要作用.无论在培养规模,还是在最终培养获得的藻生物量上,均取得了非常重要的研究进展.     

异养条件下双酚基丙烷对小球藻生长特性的影响

在1 g/L葡萄糖和BPA共同异养培养普通小球藻的情况下,考察了BPA对小球藻生长特性影响和小球藻对BPA的去除效果。结果表明,在BPA浓度10 mg/L时,可促进小球藻的异养生长,而BPA浓度大于10 mg/L时,则表现为抑制作用;单位量普通小球藻对BPA的去除速率(比去除率)与BPA浓度呈正相关关系。因此当BPA浓度为50 mg/L、培养时间为24~48 h时,BPA的最大比去除速率为3.51×10~(-7)mg/(cell·h)。普通小球藻在不同浓度BPA与1 g/L葡萄糖混合培养条件下,其生长动力学中最大比生长速率μ_(max)、最大生物量B_f值皆随BPA浓度的增加呈现先增后减的变化趋势。     

发酵罐高密度异养培养小球藻的研究

文章研究了小球藻利用发酵罐进行高密度异养培养。通过对流加培养和半连续培养两种培养方式的研究,测定小球藻Y4的生长量和油脂含量,确定藻株维持稳定生长的最优培养条件。实验结果表明,pH=7,DO=20%,补料最佳C/N为100,补料适宜碳浓度为30 g/L,取料量为1/5,小球藻Y4可以实现高密度稳定生长,且油脂含量较高,促进了小球藻高密度培养的开发和利用。     

基于废蔗渣为原料的小球藻产微生物油脂的研究

基于废蔗渣为原料,通过将蔗渣中的各类含碳有机物水解为可供小球藻吸收利用的糖类,对比两种水解方式获取更高糖浓度的蔗渣水解液,用此类方法得到的蔗渣水解液异养培养小球藻。通过测定分析小球藻的生长量、产油量、产油效率三项指标获取能有效培养小球藻产油的水解液含量。在此基础上,通过改变小球藻不同的生长条件,得到最适宜其产油的条件。结果表明:高温灭菌能增加水解液含糖量;水解液体积为到3mL即总糖浓度为0. 7200g/L时小球藻各项指标达到最大化; p H的范围对小球藻的产油影响最大,小球藻最佳产油条件为尿素含量100mmol/L,光照时长18h,p H为7。本实验方法便捷,成本低廉,具有较好的工业化应用前景,为固废回收利用及微藻产油经济化提供了参考。     

普通小球藻异养-光自养串联培养的培养基

采用单因素实验和均匀实验获得了适合于普通小球藻异养-光自养串联培养的培养基(HA-SK培养基),其关键是C/N比和保证足够的C, N供应. 采用该培养基在摇瓶中异养-光自养串联培养普通小球藻,异养培养结束时细胞密度达13.17 g/L,经过36 h光自养培养后藻体蛋白质和叶绿素含量分别达49.75%和30.17 mg/g. 用5 L生物反应器和1 L平板光生物反应器串联培养,藻细胞密度最高可达15.36 g/L,藻体蛋白质和叶绿素含量分别达54.78%和31.23 mg/g. 表明采用HA-SK培养基进行异养-光自养串联培养可实现普通小球藻的高密度高品质培养.     

基于发酵动力学模型的小球藻高密度发酵培养

构建了50 L发酵罐小球藻分批培养动力学模型,采用补料策略高密度发酵培养小球藻,考察了补料发酵过程中碳源的利用情况,采用实时荧光定量PCR技术分析了蛋白质合成关键酶二氨基庚二酸异构酶(dapF)、柠檬酸合成酶(CS)和葡萄糖?6-磷酸脱氢酶(G6PDH)的基因表达情况. 结果表明,小球藻经补料培养120 h,细胞生物量达106.65 g/L,平均生长速率为0.89 g/(L?h),葡萄糖的细胞得率为0.56 g/g,发酵过程中葡萄糖和尿素浓度对小球藻的dspF, CS和G6PDH基因表达量有重要影响.     

黄孢原毛平革菌产乙二醛氧化酶发酵条件的优化

对限氮培养基在氧环境下培养黄孢原毛平革菌(Phanerochaete chrysosporium)合成乙二醛氧化酶的条件进行了研究。结果表明:葡萄糖和酒石酸铵的组合为最佳碳、氮源组合;最佳碳源浓度为15 g/L;最佳氮源浓度为0.2 g/L;最佳接种量为3×107/50 mL;最佳通氧频率为1次/天;最佳温度为37℃。通过正交试验,确定3 mg/L维生素B1、0.05%Tween-80和5.0 mmol/L苯甲醇为最佳组合。     

Lipids of Haliphthoros philippinensis: An oomycetous marine microbe

Lipids of the marine oomycetous microbe Haliphthoros philippinensis were characterized by chromatographic and spectroscopic techniques. Total lipid content of this organism was relatively low and not very responsive to manipulation of the culture conditions. Neutral lipid comprised 21% of the total lipid and the polar lipids were mainly phosphatidylcholine (44%), phosphatidylethanolamine (15%), and a ceramide-phosphorylethanolamine (19%). Palmitic (16:0) was the primary saturated fatty acid at 25% of the total fatty acids, and arachidonic acid (20:4n-6, ARA) and eicosapentaenoic acid (20:5n-3, EPA) were the major unsaturated fatty acids at 19 and 21%, respectively. Fucosterol was the principal sterol at 59% of the total sterols. The effects of several cultivation variables on growth and EPA production by this species were investigated. Among those tested, glucose and sodium glutamate were the most efficient carbon and nitrogen sources for growth, respectively. When the mycelium was cultivated for 6 d to produce biomass under optimal growth conditions, and then transferred to low temperature for an additional 13 d without glucose, the EPA content reached 31% of the total fatty acids and the yield was 203 mg/L. When the same experiment was performed with glucose supplementation during the low-temperature phase, EPA composed 27% of total fatty acids and yield reached 316 mg/L, or a 285% increase over that from mycelium cultured for 6 d at 24°C, and 56% over that cultured at 16°C for 13 d. ARA production did not respond accordingly.     

Lipid body formation by <Emphasis Type="Italic">Thraustochytrium aureum</Emphasis> (ATCC 34304) in response to cell age

The heterotrophic marine protist, Thraustochytrium aureum produces substantial amounts of polyunsaturated fatty acids (PUFAs). In the present investigation, changes in the lipid and fatty acid profiles of T. aureum were studied according to the culture age. T. aureum was grown in artificial sea water medium for 10 days at 25 °C in shake culture condition. One to 10 day old cell samples were analyzed for cell biomass production, total lipid content, fatty acid profile and lipid body formation. In all the samples tested, total lipid production was found to be directly proportional to the dry cell weight of T. aureum. In the early phase of cell growth, cell biomass production, lipid content and glucose consumption were found to be higher. Thin layer chromatographic analysis (TLC) of lipids showed the presence of triacylglycerol (TAG; 169 mg/g, 90%), phospholipids (PL; 83 mg/g, 66%) and sterol (ST; 6 mg/g, 5%), which were recorded at maximum levels in the early growth phase of the cells. The composition of PUFAs and saturated fatty acids (SFAs) of the cell biomass and lipid class components (TAG and PL) was identified by gas chromatographic analysis (GC). In the early phase of cell growth, production of PUFAs in the total fatty acids was found to have attained maximum levels (61.3%) in which docosahexaenoic acid alone showed higher content of occurrence (99.0 mg/g in total lipid; 65.2 mg/g in TAG and 41.0 mg/g in PL). In the middle phase of cell growth, palmitic acid production was found to be higher (36.7 mg/g in total lipid; 31.3 mg/g in TAG and 12.6 mg/g in PL). Transmission electron microscopic studies of the cells showed the presence of a membrane around the lipid bodies in the early phase of cell growth. TAG and PL were actively involved in the formation of lipid bodies in the cells of T. aureum. Large-sized lipid bodies accumulated in 3 day old cells which were then fragmented into smaller bodies in the late growth phase.     

Lipid,protein and fatty acid profiles of Emericella sp. in different media

The soil‐derived fungus Emericella sp. was explored for its potential to produce lipid. Lipid profile, fatty acid composition, production of proteins and carbohydrates from lipid‐extracted biomass were determined. The effects of variations in the contents of carbon sources (glucose, dextrose), the salt content (NaCl) and the growth period were studied. A study on the effect of different growing media on the above‐mentioned parameters was also carried out. Although the maximum amount of lipid (6.14 ± 0.42 g/L) and protein (5.99 ± 0.47 g/L) was produced after 13 days in medium A containing 10% wt/vol glucose, the optimum lipid (2.90 ± 0.21 g/L) and protein (3.23 ± 0.28 g/L) production was observed in 2% wt/vol glucose medium considering the glucose content in the medium. The principal fatty acids found were 16:0 (14.4 ± 1.0 to 24.5 ± 2.4 wt‐%), 18:0 (12.1 ± 0.4 to 27.7 ± 2.7 wt‐%), 18:1 (13.5 ± 2.1 to 25.2 ± 2.8wt‐%) and 18:2 (30.9 ± 2.0 to 47.0 ± 2.8 wt‐%). Some of the lipids, especially those grown for 7 days in less glucose‐containing (1 and 2% wt/vol) medium were found to contain nearly 9.0 wt‐% of long‐chain PUFA 18:4, 20:4, 20:5, 22:4, and 22:5).     

Production of high yields of docosahexaenoic acid by Schizochytrium sp. strain SR21

The culture conditions for high-yield production of docosahexaenoic acid (DHA) by Schizochytrium sp. strain SR21 were investigated in a fermenter. With increasing carbon (glucose) and nitrogen (corn steep liquor and ammonium sulfate) sources (up to 12% glucose) in the medium, DHA productivity increased without a decrease in growth rate, i.e., 2.0, 2.7, and 3.3 g DHA/L/d with 6, 10, and 12% glucose, respectively. Eventually, 48.1 g dry cells/L and 13.3 g DHA/L were produced in 4 d with 12% glucose. DHA productivity was decreased with 15% glucose, i.e., 3.1 g/L/d. With 12% glucose, the lipid content was 77.5% of dry cells, and DHA content was 35.6% of total fatty acids. The lipid was composed of about 95% neutral lipid and 5% polar lipid. In polar lipids, the contents of phosphatidylcholine (PC), phosphatidylethanolamine, and phosphatidylinositol were 74, 11, and 5%, respectively. The PC profile was simple, 70% of PC molecules were 1-palmitoyl-2-DHA-PC and 1.2-di-DHA-PC. These results indicate that Schizochytrium sp. strain 21 is an excellent source for microbial DHA production, including not only the acid form of DHA but also 2-DHA-PC.     

Effect of culture conditions on fatty acid composition in lipids produced by the yeastcryptococcus albidus var. albidus

The influence of culture conditions on the fatty acid composition in lipids produced by Cryptococcus albidus var. albidus CBS 4517 was studied. The major fatty acids in C. albidus var. albidus were oleic (18:1), linoleic (18:2) and palmitic (16:0) acid. The relative amounts of fatty acids produced varied considerably during growth and lipid accumulation phases in nitrogen-limited as well as excess-nitrogen cultures. The degree of unsaturation correlated to the lipid content in the biomass and decreased with increasing amounts of cellular lipid. After glucose exhaustion, no further changes in the fatty acid composition nor in the lipid content of the cells were observed. A number of carbon and nitrogen sources could be utilized for lipid synthesis, but they influenced the fatty acid composition only to a minor extent.     

Effects of various carbon and nitrogen sources on fungal lipid production

The efficiency of lipid production byTolyposporium ehrenbergii andSpacelotheca reiliana (family Ustilaginaceae) cultivated on a fat-free medium was evaluated. The fungi were artificially cultured on media containing various monoor disaccharides and urea or peptone as basic sources for carbon and nitrogen, respectively. Some natural and industrial byproducts (glycerol, glucose syrup, potato hydrolysate and molasses hydrolysate) were also used as principal carbon sources for fungal growth. Media containing fructose/peptone or glucose/peptone were the most efficient for fungal fat production during one week of incubation. After a two-week incubation period, highest phospholipid concentrations were found in S.reiliana andT. ehrenbergii mycelia obtained from media containing molasses hydrolysate/peptone and glycerol/urea, respectively. Fatty acid analysis of the fungal growth indicated the presence of a wide range of fatty acids, i.e., odd-and even-carbon numbered acids, both saturated and unsaturated. The results demon-strated that the variability in the fatty acid composition largely depends on the type of sugar and nitrogen sources and the age of the culture.     

Eicosapentaenoic acid and docosahexaenoic acid production potential of microalgae and their heterotrophic growth

Twenty microalgal strains were investigated in photoautotrophic flask cultures for their potential for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) production. The highest EPA proportion (% of total fatty acids) was produced by Monodus subterraneus UTEX 151 (34.2%), followed by Chlorella minutissima UTEX 2341 (31.3%) and Phaeodactylum tricornutum UTEX 642 (21.4%). The highest DHA proportion (% of total fatty acids) was obtained in Crypthecodinium cohnii UTEX L1649 (19.9%), followed by Amphidinium carterae UTEX LB 1002 (17.0%) and Thraustochytrium aureum ATCC 28211 (16.1%). Among the 20 strains screened, the EPA yield was high in M. subterraneus UTEX 151 (96.3 mg/L), P. tricornutum UTEX 642 (43.4 mg/L), Chl. minutissima UTEX 2341 (36.7 mg/L), and Por. cruentum UTEX 161 (17.9 mg/L) owing to their relatively high biomass concentrations. The DHA yield was high in C. cohnii UTEX L1649 (19.5 mg/L) and A. carterae UTEX LB 1002 (8.6 mg/L). Heterotrophic growth of these 20 microalgae was also tested on two different carbon sources, acetate and glucose. All microalgae except Nannochloropsis oculata UTEX LB 2164 showed growth on glucose (5 g/L) under heterotrophic conditions. Twelve of them could grow heterotrophically when acetate (1 g/L) was used as their sole carbon and energy source.     

Revealing the Phenotypic and Genomic Background for PHA Production from Rapeseed-Biodiesel Crude Glycerol Using Photobacterium ganghwense C2.2

Polyhydroxyalkanoates (PHA) are promising biodegradable and biocompatible bioplastics, and extensive knowledge of the employed bacterial strain’s metabolic capabilities is necessary in choosing economically feasible production conditions. This study aimed to create an in-depth view of the utilization of Photobacterium ganghwense C2.2 for PHA production by linking a wide array of characterization methods: metabolic pathway annotation from the strain’s complete genome, high-throughput phenotypic tests, and biomass analyses through plate-based assays and flask and bioreactor cultivations. We confirmed, in PHA production conditions, urea catabolization, fatty acid degradation and synthesis, and high pH variation and osmotic stress tolerance. With urea as a nitrogen source, pure and rapeseed-biodiesel crude glycerol were analyzed comparatively as carbon sources for fermentation at 20 °C. Flask cultivations yielded 2.2 g/L and 2 g/L PHA at 120 h, respectively, with molecular weights of 428,629 g/mol and 81,515 g/mol. Bioreactor batch cultivation doubled biomass accumulation (10 g/L and 13.2 g/L) in 48 h, with a PHA productivity of 0.133 g/(L·h) and 0.05 g/(L·h). Thus, phenotypic and genomic analyses determined the successful use of Photobacterium ganghwense C2.2 for PHA production using urea and crude glycerol and 20 g/L NaCl, without pH adjustment, providing the basis for a viable fermentation process.