糖碳源和氨基酸氮源对苍白杆菌属发酵产生物表面活性剂的影响

该实验为优化苍白杆菌(Ochrobactrum sp.)产生物表面活性剂的发酵条件,比较了不同糖碳源(蔗糖、乳糖、甘油、木糖、果糖)、氨基酸氮源(谷氨酸、天冬氨酸、赖氨酸、精氨酸和缬氨酸)、碳氮比(C/N)(1、10、20、30、40)对生物表面活性剂发酵的影响。结果表明,最优碳源为蔗糖,发酵5 d达最大乳化活性56.30%;最优氮源为天冬氨酸,发酵4 d达最大乳化活性54.00%;最优C/N为10,发酵4 d达最大乳化活性55.75%。

Synthesis of Li_2Fe_(0.9)Mn_(0.1)SiO_4/C composites using glucose as carbon source

Li2Fe0.9Mn0.1SiO4/C composites were synthesized by using X-ray diffractometry （XRD）, scanning electron microscopy （SEM） glucose as carbon source. The samples were characterized by and electrochemical measurements. All Li2Fe0.9Mn0.1SiO4/C composites are of the similar crystal structure. With increasing the carbon content in the range of 5%-20% （mass fraction）, the diffraction peaks in XRD patterns broaden and the particle sizes and the tap density of samples decrease. The Li2Fe0.9Mn0.1SiO4/C composites with carbon content of 14.12% show excellent electrochemical performances with an initial discharge capacity of 154.7 mA.h/g at C/16 rate, and the capacity retention remains 92.2% after 30 cycles.

Enhanced Biological Phosphorus Removal in Anaerobic/Aerobic Sequencing Batch Reactor Supplied with Glucose as Carbon Source

Phosphorus removal performance in an aerobic/aerobic sequencing batch reactor (SBR) supplied with glucose as carbon source was investigated. It was found that there was no phosphate release concomitant with the storing of poly-β-hydroxyalkanoate (PHA) during the anaerobic phase. Whereas, glycogen was soon built up followed by rapid consumption, at the same time, glucose was depleted rapidly. Based on the analysis of different fractions of phosphorus in activated sludge, the relative ratio of organically bound phosphorus in sludge changed at the end of anaerobic and aerobic phases. The ratios were 45.3% and 51.8% respectively. This showed that the polyphosphate broke down during the anaerobic phase to supply part of energy for PHA synthesis. The reason why there was no phosphate release might be the biosorption effect of extracellular exopolymers (EPS). It was also proved by the analysis of EPS with scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). The phosphorus weight percentage of EPS at the end of anaerobic phase was 9.22%.

Nitrogen Removal Efficiencies for Two Biological Nutrient Removal （BNR） Plants in Thailand： Molasses as an External Carbon Source for Enriched Denitrifying Culture in a BNR Process

Two biological nutrient removal （BNR） wastewater treatment plants （WWTPs） in Thailand were selected for study： the Nonghkaem WWTP and the Suvarnabhumi Airport WWTP. For each site the influents, effluents, and supernatant liquids from anaerobic sludge digesters were analyzed for total Kjeldahl nitrogen （TKN）, total nitrogen （TN）, total chemical oxygen demand （TCOD）, biodegradable chemical oxygen demand （bCOD）, and biochemical oxygen demand （BOD）. Nitrogen removal efficiencies in the Nonghkaem WWTP and the Suvarnabhumi Airport WWTP were evaluated. Inadequate nitrogen removal at the Nonghkaem centralized WWTP was found during the summer period. Influent ratios of bCOD：N at the Nonghkaem plant and the Suvarnabhumi Airport plant were 2.42：1-5.45：1 and 4.1：1-6.5：1, respectively. The efficacy of addition of molasses as a carbon source for enriched denitrifying culture in a BNR process at Nonghkaem was studied. Fluorescent in situ hybridization technique （FISH） was used to identify specific nitrifying bacteria （Nitrosomonas spp., Nitrobacter spp. and Nitrospira spp.）. Nitrospira spp. was the most prevalent species in the aeration tank at the Nonghkaem WWTP. This result from FISH suggests that there were significantly low oxygen and nitrite concentration in the aeration tank at the Nonghkaem WWTP during a period of low nitrogen removal.

Production and Recovery of Rhamnolipids Using Sugar Cane Molasses as Carbon Source

Biosurfactants were synthesized by Pseudomonas aeruginosa （P.A.）, using sugar cane molasses as carbon source. Assays were conducted in a shaker with agitation speed of 200 rpm, temperature of 38 ℃ and aeration ratio （Vm/Vf） of 0.4 and 0.6. A concentration of 3.0% was used for the carbon and energy source （molasses） and of 0.3% for the nitrogen source （NaNO3）. Samples were removed at regular times until 96 hours of cultivation. The reduction in surface tension was measured using the ring method; cell concentration was obtained by the dry mass and substrate consumption by the DNS method. The metabolite produced was extracted and quantified by the thioglycolic method. The results showed a maximum surface tension reduction of 46.57% after 60 h, 3.63 g/L of biomass after 8 h （μXmax =0.15 h^-1）, 79.60% of substrate consumption （μs= 0.67 h-1） and 4.47 g/L of rhamnolipid （μp=0.029 h^-1）.

Effect of carbon source on growth and lipid accumulation in Chlorella sorokiniana GXNN01

Heterotrophic culture of microalgae to develop methods of increasing biomass productivity and storage lipids has brought new insight to commercial biodiesel production. To understand the relationship between heterotrophy and lipid production, the effects of carbon sources on the growth and lipid accumulation of Chlorella sorokiniana GXNN01 was studied. The alga exhibited an increased growth rate in response to the addition of carbon sources, which reached the stationary phase after 48 h at 30℃. In addition, glucose and NaAc had a significant effect on the lipid accumulation during the early-stationary phase. Specifically, the lipid content was 0.237±0.026 g ·g^-1 cell dry weight and 0.272±0.041 g Ll when glucose was used as the carbon source, whereas the lipid content reached 0.287±0.018 g ·g^-1 cell dry weight and 0.2884-0.008 g Lz when NaAc was used as the carbon source. The neutral lipid content was found to first decrease and then increase over time during the growth phase. A glucose concentration of 20 mmol L^-1 gave the maximal lipid yield and the optimum harvest time was the early-stationary phase.