Influence of Substrate Feeding and Process Parameters on Production of Coenzyme Q₁₀Using <i>Paracoccus denitrificans</i>ATCC 19367 Mutant Strain P-87

Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Constructing the high-yielding CoQ10 producing strains is a pre-requisite for cost-effective production. A superior mutant strain P-87 generated from Paracoccus denitrificans ATCC 19367, which showed 1.25-fold improvement in specific CoQ10 content higher than the wild type strain at shake flask level, was selected to carry out the studies on CoQ10 yield improvement through fermenter process optimization. In the course of study, initially the cane-molasses-based medium and fed-batch fermentation strategy using pHBA in combination with sucrose were standardized in shake flask using wild type strain. This strategy was subsequently translated at 2 L laboratory fermenter while optimizing the fermentation process parameters using improved mutant strain P-87. Under optimized fermentation condition, mutant strain P-87 produced 49.85 mg/L of CoQ10 having specific content of 1.63 mg/g of DCW, which was 1.36 folds higher than the specific CoQ10 content of wild-type strain under similar optimized condition. The temperature and DO were found to be critical parameters for CoQ10 production by mutant strain P-87. The optimum temperature was found to be 32°C and the optimum DO concentration to be maintained throughout the fermentation cycle was found to be 30% of air saturation. Overall, a new cost-effective process has been established for the production of CoQ10 using the cheaper substrate “cane molasses” and higher CoQ10 producing mutant strain P-87.

Study on Strontium Mineralization by Thiobacilus Denitrificans for Remediation

1 Introduction Radioactive pollution is increasingly serious and radioactive pollution can not be repaired immediately once it breaks out.Strontium contamination is a research hot point as one of the typical radioactive pollution,and

Identification and Metabolic Mechanism of Non-fermentative Short-cut Denitrifying Phosphorus-removing Bacteria

To investigate the characteristics and metabolic mechanism of short-cut denitrifying phospho- rus-removing bacteria （SDPB） that are capable of enhanced biological phosphorus removal （EBPR） using nitrite as an electron acceptor, an aerobic/anoxic sequencing batch reactor was operated under three phases. An SDPB-strain YC was screened after the sludge enrichment and was identified by morphological, physiological, biochemical properties and 16S rDNA gene sequence analysis. Denitrifying phosphorus-removing experiments were conducted to study anaerobic and anoxic metabolic mechanisms by analyzing the changes of chemical oxygen demand （COD）, phosphate, nitrite, poly-fl-hydroxybutyrate （PHB）, and glycogen. The results show that strain YC is a non-fermentative SDPB similar to Paracoccus denitrificans. As a kind of non-fermentative bacteria, the energy of strain YC was mainly generated from phosphorus release （96.2%） under anaerobic conditions with 0.32 mg P per mg synthesized PHB. Under anoxic conditions, strain YC accumulated 0.45 mg P per mg degraded PHB, which produced most of energy for phosphate accumulation （91.3%） and a little for glycogen synthesis （8.7%）. This metabolic mechanism of strain YC is different from that of traditional phosphorus-accumulating organisms （PAOs）. It is also found that PHB, a kind of intracellular polymer, plays a very important role in denitrifying and accumulating phosphorus by supplying sufficient energy for phosphorous accumulation and carbon sources for denitrification. Therefore, monitoring AP/APHB and ANO2 -N/APHB is more necessary than monitoring AP/ACOD, ANO2 -N/ACOD, or AP / ANO2 -N.

Tentative Study on a New Way of Simultaneous Desulfurization and Denitrification

Thiobacillus denitrificans, a kind of autotrophic facultative bacteria, can oxidize sulfide into elemental sulfur or sulfate when nitrate was adopted as its electron accepter and carbon dioxide as its carbon resource under anoxic or anaerobic environment. In this way, nitrate is converted into nitrogen. In addition, ThiobaciWus denitrificans can accumulate sulfur extracellularly. In this study, in a process of simultaneous desulfurization and denitrification, a strain of Thiobacillus denitriificans is employed as sulfur-producer in the treatment of wastewater containing sulfide and nitrate. The key factors affecting this process are investigated through batch tests. The experimental results indicate that the sulfide concentration and the ratio of sulfide to nitrate (S2-/NO3-) in the influent are the key factors, and their suitable values are suggested to be 5/3 and no more than 300mg·L-1, respectively, in order to achieve high conversion of sulfur.

典型湿地环境条件下Shewanella介导N2O产生机制及意义

利用湿地中高丰度的代表性反硝化菌Shewanella denitrificans,文章通过批式实验,探究典型湿地环境条件下pH和C/N对微生物反硝化排放N2O的影响和机制。结果表明,在典型湿地环境条件下,S.denitrificans介导的反硝化均能排放N2O温室气体。其中,当C/N为7.5或75时N2O排放速率最快,比最低排放速率高出约54%。当pH为5.5时,N2O排放速率较pH为6.5时增加约67%。不同pH和C/N条件下N2O的排放差异可能主要由p H差异导致,或p H和C/N差异共同所致。双因素方差分析结果表明,pH和C/N不仅分别显著影响N2O排放,并且两者对N2O排放具有显著的交互影响。这些发现为湿地生态系统N2O排放的模型构建和评估预测提供了科学依据。

高效异养硝化-好氧反硝化菌株TS-1筛选及降解特性

从实验室定向驯化的活性污泥中分离筛选出一株具有异养硝化-好氧反硝化功能的菌株TS-1.通过生理生化及16S r RNA基因序列鉴定其为脱氮副球菌,通过单因素和正交实验对其去除NH4+-N的最佳条件进行优化,并通过对比进一步探究其在不同氮源条件下对各形态无机氮的去除规律.结果表明该菌株最适碳源为丁二酸钠,最佳C/N为15,最佳接种量为5%,最适温度为30℃、p H为8.0.以初始浓度约为100 mg/L的NH4+-N、NO3--N和NO2--N分别为单一氮源时,菌株TS-1对各形态氮的去除率为97.49%、100%和95.94%;维持各形态氮初始浓度不变,将其两两混合时发现混合氮源中若包含NO2--N会使菌株OD600值达到最大值所用时间延长,氮源中含有NH4+-N会降低菌株对其他形态氮源的去除率,以及NO3--N的添加会使菌株对NH4+-N的去除能力降低;3种形态氮源同时存在的条件下,该菌对各氮源去除能力由强至弱为NO2--N>NH4+-N>NO3--N.本研究从活性污泥中分离筛选出一株具有高效异养硝化-好氧反硝化功能的菌株TS-1,通过研究碳源、氮源、温度、p H得到了最佳降解条件,可为废水短程脱氮提供参考.(图9表4参37)