【作者】 黄勇；

【导师】 黄云；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2017， 硕士

【摘要】 随着全球化石能源急剧减少及环境污染问题日益加剧,发展绿色可再生能源已经成为解决能源环境危机的重要突破口。微藻生物质作为第三代生物质能源,源于其光合效率高、生长周期短、油脂含量高、环境适应性强等优点,是一种极具潜力的新型生物质原料。由于微藻生物膜内CO2和光传输阻力相对较小,其内微藻的光合作用效率高,且生物膜具有操作稳定、采收方便等优点,相比于悬浮态微藻培养具有更大优势。因此本文以亲水性有机尼龙微孔滤膜作为微藻生物膜吸附材料,对微藻进行生物膜培养。对比了两种培养形态下光合自养与光合自养-异养生物膜在生物膜生长产油特性和生物膜微观形态方面的差异性。从光传递角度研究了培养基循环流动式培养下光强、初始接种面积密度对光合自养-异养生物膜生长产油特性的影响。从营养物质角度研究了培养基循环流动式培养下营养物质浓度、培养基间歇供给、异养加入时间对光合自养-异养生物膜生长产油特性的影响。全文主要结论如下:(1)光合自养与光合自养-异养微藻生物膜的细胞直径随着生长逐渐变大,光合自养-异养生物膜的细胞平均直径要比光合自养生物膜的细胞平均直径大17.1%;在生物膜形态上光合自养-异养生物膜要比光合自养生物膜疏松多孔。以琼脂固化的固体培养基为营养基底时,光合自养-异养生物膜前两天生长速率要高于光合自养生物生长速率,光合自养-异养生物膜前两天的生长速率是光合自养的2.28倍;光合自养-异养微藻生物膜的油脂产量为10.31 g/m2,是光合自养油脂产量的1.91倍。而以流动式液体培养基输送营养时,光合自养-异养生物膜第一天生长速率也要高于光合自养生物生长速率,且比固化培养基的要高但最终生物膜面积密度要低,光合自养-异养的生长速率是光合自养的4.04倍;光合自养-异养的油脂产量为20.12 g/m2,是光合自养油脂产量(9.08 g/m2)的2.22倍。(2)以琼脂固化的固体培养基为营养基底时,发现光合自养-异养微藻生物膜的光饱和点为150μmol/m2/s,过高的光强会对微藻生物膜产生抑制,使其分解色素以致细胞变白最终生物膜面积密度下降。而在物质传输阻力方面,光合自养-异养微藻细胞无法吸收固化培养厚度大于10 mm处的营养物质,光合自养-异养微藻生物膜在4倍于基底培养基的无机盐浓度下油脂产量最高(22.01 g/m2),表明光合自养-异养生物膜能耐受更高倍数的无机盐;而葡萄糖这种相对无机盐离子从固化培养基靠毛细力作用扩散作用传递到滤膜上再传递到生物膜内过程中传递阻力大,致使传递进生物膜内的葡萄糖量相对较少,对生物膜内微藻异养比例小,进而油产量差别不大。(3)在流动的液态培养基为营养基底时,相对于琼脂固化的固体培养基为营养基底,微藻生物膜的含水量高,光传输能力降低,光合自养-异养生物膜内微藻的光饱和点提高至为190μmol/m2/s。生物膜生长初始,由于生物膜内与膜外的营养物质浓度梯度大,营养物质的传输速度快,生物膜内的营养物质充足,生长速率快,致使前1~2天微藻生物膜生长速率快,且微藻初始生长速率随初始接种面积密度的增加而增加,而由于异养代谢水增加了生物膜内物质传输阻力,后期生长速率降低,尤其是在低倍数(0.5倍)无机盐浓度低,光合作用强度相对较弱,生物膜内微藻异养比例大,异养产生的水越多,对生物膜生长越不利。(4)生物膜内微藻油脂含量随异养底物葡萄糖浓度从1g/L增加10g/L而增加至43.67%,且微藻生物膜生物质密度同时增加,同步光合自养-异养下实现了微藻生物质密度和油脂含量同步增加,解决了微藻生长和油脂积累相互矛盾不同步的问题。而由于异养会代谢出水,增加生物膜的含水量,使得物质传输阻力增加,因此为了减少生成水的影响,采用先光合自养富集一定的生物膜密度后再开启异养辅助的方法,发现当光合自养生物膜密度增加到57.48 g/m2时,开启异养辅助后生物膜面积密度最高达104.36 g/m2,油脂产量也最高达26.17 g/m2,也实现了高效的生物质和油脂的同时积累。培养基间歇供给对第1天的生物膜生长速率影响比较大,对细胞内的色素、油脂化合物含量影响不大。更多还原

【Abstract】 With the rapid reduction of global fossil fuels and the increasing problem of environmental pollution,the development of green renewable energy has become an important breakthrough to solve the energy and environmental crisis.Microalgae biomass as a third generation of biomass energy,from its high photosynthetic efficiency,short growth cycle,high lipid content,environmental adaptability,etc.,is a great potential for new biomass raw materials.Because of the relatively small CO2 and light transmission resistance in microalgae biofilm,the photosynthetic efficiency of microalgae is high,and the biofilm has the advantages of stable operation and convenient harvesting,which has a greater advantage than that of suspended microalgae culture.Therefore,the hydrophilic organic nylon microporous membrane as microbial biofilm attachment material,the microalgae biofilm culture.The differences of phototrophy and phototrophy-heterotrophy biofilm in the biofilm growth and the microstructure of biofilm were compared.The effects of light intensity and initial inoculation area density on the lipid-producing characteristics of phototrophy-heterotrophy biofilm were studied from the perspective of light transmission.The effects of nutrient concentration,intermittent supply of culture medium and heterotrophy time on the lipid-producing characteristics of phototrophyheterotrophy biofilm were studied from the perspective of nutrient.The main conclusions are as follows:(1)The cell diameter of the phototrophy and phototrophy-heterotrophy microalgae biofilm increased gradually with the growth.The average diameter of the phototrophyheterotrophy biofilm was 17.1% higher than that of the phototrophy biofilm.The phototrophy-heterotrophy microalgae biofilm was more porous than the phototrophy biofilm in biofilm morphology.When the agar-solidified medium was used as the nutrient substrate,the growth rate of phototrophy-heterotrophy biofilm was higher than that of phototrophy growth rate.The two-day growth rate of phototrophy-heterotrophy biofilm was 2.28 times higher than that of phototrophy.The lipid yield of phototrophyheterotrophy microalgae biofilms was 10.31 g/m2,which was 1.91 times higher than that of phototrophy.The growth rate of phototrophy-heterotrophy biofilm was higher than that of phototrophy growth rate and higher than that of curing medium,but the final biofilm area density was lower than that of solidified medium.The lipid yield of phototrophyheterotrophy biofilm was 20.12 g/m2,which was 2.22 times higher than that of phototrophy(9.08 g/m2).(2)When the agar solidified medium was used as the nutrient substrate,it was found that the light saturation point of the phototrophy-heterotrophy microalgae biofilm was 150 μmol/m2/s.The high light intensity could inhibit the microalgae biofilm.Its decomposition of the pigment so that the cell become white and biofilm density decreased.In the aspect of material transmission resistance,the phototrophy-heterotrophy microalgae cells could not absorb the nutrient with the thickness of more than 10 mm.The phototrophy-heterotrophy microalgae biofilm had the highest lipid yield(22.01 g/m2)at 4 times the inorganic salt concentration of the basal medium,indicating that the phototrophy-heterotrophy biofilm can tolerate a higher times of inorganic salts.Glucose relative to the inorganic salt ions have a greater transmission resistance,resulting in the amount of glucose transferred into the biofilm is relatively small,the biofilm microalgae heterotrophy ratio is small,and then the lipid yield is not significant.(3)When the mobile liquid medium is a nutrient base,the solid culture medium is agar-solidified,and the microflora biofilm has high water content and low light transmission ability.The saturation point of phototrophy-heterotrophy biofilm is increased to 190 μmol/m2/s.Biofilm growth initial,due to biofilm inside and outside concentration gradient,the rapid transmission of nutrients,biofilm nutrient sufficient,the growth rate is fast,resulting in the first 1 to 2 days microalgae biofilm growth rate.The initial growth rate of microalgae increased with the increase of initial inoculation area density.As heterotrophic water increased the transport resistance of biofilm,the later growth rate decreased,especially at low times(0.5 times)inorganic salt concentration low,photosynthetic intensity is relatively weak,biofilm microalgae heterotrophic ratio is large,the more water produced by heterotrophy,the more unfavorable to biofilm growth.(4)The lipid content of microalgae biofilm increased to 43.67% with heterotrophic substrate glucose concentration the increase of 1 g/L to10 g/L,and the microalgae biofilm area density increased at the same time.Simultaneous phototrophy-heterotrophy to achieve a simultaneous increase in microalgae biomass and lipid content,to solve the microalgae growth and accumulation of lipid is not contradictory problems.And because the heterotrophic metabolism of water,increase the water content of biofilm,making the material transmission resistance increased.In order to reduce the impact of the formation of water,using the first phototrophy and enrichment of a certain biofilm area density and then open the heterotrophy auxiliary method,in order to reduce the water production.It was found that when the density of phototrophy biofilm area density increased to 57.48 g/m2,the density of biofilm was up to 104.36 g/m2 and the lipid yield was up to 26.17 g/m2,also to achieve a high degree of accumulation the biomass and lipid at the same time.The intermittent supply of medium had a great effect on the growth rate of biofilm on day 1,but had little effect on the pigment and lipid compounds contents in the cells.更多还原