Photofermentative hydrogen production from molasses: Scale-up and outdoor operation at low carbon-to-nitrogen ratio

Photofermentative hydrogen production was carried out under outdoor conditions with a Rhodobacter capsulatus strain on molasses, a renewable and sustainable feedstock. An existing photobioreactor design was scaled-up from 9 L to 20 L. The decreased carbon-to-nitrogen (C/N) ratio of 13.0, compared to our previous work, accelerated growth and resulted in a reduced lag period for hydrogen production as well as higher productivities in the exponential phase. However, the low C/N ratio also promoted a high optical density due to growth, limiting light transmission. Still, the maximum productivity was found as 0.47 mol H₂/(m³·h), significantly higher than our result with the smaller reactor volume. High rates of production could not be maintained presumably due to the combined effects of cloudy periods, the aforementioned C/N ratio and decreasing pH. These results suggest that the scale-up was successful and there is potential for further improvement using optimal C/N ratio and cell concentration values.     

Freeze drying and vacuum impregnating characteristics of Nostoc sphaeroides Kützing

ABSTRACT

Nostoc sphaeroides Kützing (N. sphaeroides) is a kind of edible algae widely growing in China. The paper is aimed at developing a novel snack food of N. sphaeroides using vacuum impregnation. The samples from freeze drying (FD) have large volume and loose structure, which were found suitable for processing. With nuclear magnetic resonance and imaging, the water signal of N. sphaeroides was measured in FD, and different drying-stage raw N. sphaeroides were selected to impregnate by different solutions, when the products’ impregnated mass, water activity, and flavor difference were analyzed. Results indicate that the water distribution in FD was uniform. Sucrose impregnated product was stable with large impregnated mass and low water activity, whereas trehalose impregnated product was easy to separate from the solution with low sweetness. For the products with the raw N. sphaeroides dried for 9 and 12?h, no obvious difference was found in water activity and flavor. Result shows that N. sphaeroides dehydrated for 9?h in FD is suitable for vacuum impregnation, and different impregnated products are acceptable from the point of view of flavor and storage stability.     

Photoactive Electrodes Incorporating Electrosprayed Bacterial Reaction Centers

Highly efficient light absorption and charge separation within the photosystem and reaction center (RC) complexes of photosynthetic plants and bacteria are of great interest for solar cell and photo detector applications, since they offer almost unity quantum yield and expected ultimate power conversion efficiencies of more than 18% and 12%, respectively. In addition, the charge separated states created by these protein complexes are very long lived compared to conventional semiconductor solar cells. In this work, a novel technique is presented for the deposition of photosynthetic protein complexes, by electrospraying RCs of Rhodobacter sphaeroides onto highly ordered pyrolytic graphite (HOPG) electrodes. Remarkably, it is shown that the RCs not only survive exposure to the high electric fields but also yield peak photocurrent densities of up to 7 μA cm^?2, which is equal to the highest value reported to date.     

球形红细菌降解PNP的不同因素影响及代谢机理

通过拟合Haldane动力学方程,分析球形红细菌(Rhodobacter sphaeroides)H菌株降解对硝基苯酚(PNP)的生长动力学特性;考察营养因素(碳源、金属离子和NaCl浓度)对H菌株降解PNP的影响以及H菌株对酚类物质的底物广谱性,并对H菌株降解PNP的代谢机理进行推测。结果表明,H菌株降解PNP的生长动力学符合Haldane模型(R~2=0.9990);H菌株降解PNP的最适碳源和金属离子分别是苹果酸和Ca~(2+),NaCl浓度耐受值为20 mg·L-1;酚类物质中邻苯二酚对PNP降解影响最大;利用高效液相色谱-质谱联用仪(HPLC-MC)对菌株代谢PNP的产物进行分析,发现中间产物主要为对苯二酚(HQ)、4-羟基粘糠酸半醛(4-HS)和马来酰胺乙酸(MA),同时酶活性分析表明底物HQ在粗酶液中对苯二酚1,2-双加氧酶作用下生成4-HS,由此推测H菌株可能利用的是对苯二酚代谢途径。     

Hydrogen production from rotten dates by sequential three stages fermentation

This study was devoted for H₂ production from rotten fruits of date palm (Phoenix dactylifera L.) by three fermentation stages. A facultative anaerobe, Escherichia coli EGY was used in first stage to consume O₂ and maintain strict anaerobic conditions for a second stage dark fermentative H₂ production by the strictly anaerobic Clostridium acetobutylicum ATCC 824. Subsequently, a third stage photofermentation using Rhodobacter capsulatus DSM 1710 has been conducted for the H₂ production. The maximum total H₂ yield of the three stages (7.8 mol H₂ mol⁻¹ sucrose) was obtained when 5 g L⁻¹ of sucrose was supplemented to fermentor as rotten date fruits. A maximum estimated cumulative H₂ yield of the three stages (162 LH₂ kg⁻¹ fresh rotten dates) was estimated at the (5 g L⁻¹) sucrose concentration. These results suggest that rotten dates can be efficiently used for commercial H₂ production. The described protocol did not require addition of a reducing agent or flashing with argon which both are expensive.     

类球红细菌突变株及其应用

本研究以类球红细菌1.1737为出发菌株,经空间搭载实验,从回收样品中筛选得到了一株颜色变浅的类球红细菌突变株,利用高效液相色谱分析发现该突变株的辅酶Q10产量较出发菌株提高了30.4%。另外柱层析提纯的结果显示突变株发酵液的分离效率优于出发菌株。     

高产辅酶Q10类球红细菌的化学诱变筛选及其发酵培养基优化

利用菌株对（维生素K3+叠氮化钠+对羟基苯甲酸）的复合抗性作为筛选标记,对产辅酶Q10的类球红细菌（Rhodobacter sphaeroides）使用亚硝基胍进行化学诱变,筛选高产菌株并采用响应面法优化其发酵培养基。结果表明,经诱变选育得到一株遗传稳定的辅酶Q10高产菌株R.sp3-7,其最佳发酵培养基组成为：葡萄糖31.7 g/L,玉米浆干粉5.6 g/L,（NH4）2SO4 5.3 g/L、谷氨酸钠 3.0 g/L、NaCl 3.0 g/L、MgSO4·7H2O 12.5 g/L、KH2PO4 3.0 g/L、CaCO3 2.0 g/L、辅液1 mL/L。在此培养条件下,诱变菌株R.sp3-7的辅酶Q10产量达（93.63±0.59） mg/L,与出发菌株相比提高了116.8%。 关键词：中图分类号：TS201.3 文章编号：0254-5071（20１6）06-0090-06 doi:     

Statistical optimization of biohydrogen production from sucrose by a co-culture of Clostridium acidisoli and Rhodobacter sphaeroides

Statistically based experimental designs were applied to optimize the fermentation process parameters for hydrogen (H₂) production by co-culture of Clostridium acidisoli and Rhodobacter sphaeroides with sucrose as substrate. An initial screening using the Plackett–Burman design identified three factors that significantly influenced H₂ yield: sucrose concentration, initial pH, and inoculum ratio. These factors were considered to have simultaneous and interdependent effects. A central composite design and response surface analysis were adopted to further investigate the mutual interactions among the factors and to identify the values that maximized H₂ production. The optimal substrate concentration, initial pH, and inoculum ratio of C. acidisoli to R. sphaeroides were 11.43 g/L sucrose, 7.13, and 0.83, respectively. Using these optimal culture conditions, substrate conversion efficiency was determined as 10.16 mol H₂/mol sucrose (5.08 mol H₂/mol hexose), which was near the expected value of 10.70 mol H₂/mol sucrose (5.35 mol H₂/mol hexose).     

野生葛仙米营养成分分析及评价

本文以野生葛仙米为原料,研究了葛仙米营养成分及组成并对其进行营养评价。结果表明:野生葛仙米蛋白质含量达48.61%,含17种氨基酸,其中含人体7种必需氨基酸为44.619%;脂肪酸含量为8.11%,以中碳链为主;富含维生素,VB11.2mg/100g,VB211.8mg/100g,VC550mg/100g,VE7.0mg/100g,β-胡萝卜素114mg/100g,是一种珍稀的食用资源和可开发的蛋白源。