Effects of bacteriophage on the surface properties of chalcopyrite (CuFeS₂), and phage-induced flocculation of chalcopyrite, glacial till, and oil sands tailings

The binding of mineral-specific phage to the surface of chalcopyrite (CuFeS(2)) was investigated by using X-ray photoelectron spectroscopy and scanning Auger microscopy. These studies confirmed the elemental composition of the minerals and confirmed that bacteriophage were bound to the mineral surface. These techniques also revealed that the phage were not forming a continuous film over the entire surface of the CuFeS(2) particles, but selectively bound to the slimes coating the particles. In addition, the effect of mineral-specific phage binding to the surface of CuFeS(2) was investigated using induction time and zeta potential measurements. Bacteriophage (10(12) /mL) increased the induction time (contact time resulting in 50% particle attachment to a bubble) from ～7.5 to ～17 ms and reversed the zeta potential from negative to positive. In the course of performing the zeta potential measurements on particles <45 μm in diameter, phage-induced aggregation was observed. The mechanism of aggregation was explored using a range of pH (3-11) and cation concentrations. Aggregation was observed across the tested pH range and with all cations. Phage also mediated aggregation of glacial till and oil sands tailings in a dose-dependent and particle size-dependent manner. We conclude that binding of bacteriophage to the surface of CuFeS(2) does alter its surface properties.     

Evaluation of electro‐coagulation–flocculation for harvesting marine and freshwater microalgae

Although microalgae are considered as a promising feedstock for biofuels, the energy efficiency of the production process needs to be significantly improved. Due to their small size and low concentration in the culture medium, cost‐efficient harvesting of microalgae is a major challenge. In this study, the use of electro‐coagulation–flocculation (ECF) as a method for harvesting a freshwater (Chlorella vulgaris) and a marine (Phaeodactylum tricornutum) microalgal species is evaluated. ECF was shown to be more efficient using an aluminum anode than using an iron anode. Furthermore, it could be concluded that the efficiency of the ECF process can be substantially improved by reducing the initial pH and by increasing the turbulence in the microalgal suspension. Although higher current densities resulted in a more rapid flocculation of the microalgal suspension, power consumption, expressed per kg of microalgae harvested, and release of aluminum were lower when a lower current density was used. The aluminum content of the harvested microalgal biomass was less than 1% while the aluminum concentration in the process water was below 2 mg L⁻¹. Under optimal conditions, power consumption of the ECF process was around 2 kWh kg⁻¹ of microalgal biomass harvested for Chlorella vulgaris and ca. 0.3 kWh kg⁻¹ for Phaeodactylum tricornutum. Compared to centrifugation, ECF is thus more energy efficient. Because of the lower power consumption of ECF in seawater, ECF is a particularly attractive method for harvesting marine microalgae. Biotechnol. Bioeng. 2011;108: 2320–2329. © 2011 Wiley Periodicals, Inc.     

壳聚糖絮凝蛹虫草菌丝体多糖工艺优化及其失活动力学分析

利用响应面法对蛹虫草诱变菌株CSYB-2菌丝体多糖的制备工艺进行优化,结果显示在壳聚糖用量1.4mL/g、絮凝温度55℃、絮凝时间70min条件下,多糖保留率为(82.05±0.21)%。在壳聚糖絮凝诱变菌株CSYB-2菌丝体多糖浸提液的絮凝工艺基础上,通过构建壳聚糖失活动力学模型,探究絮凝剂（壳聚糖）在絮凝过程中的动力学规律和失活机理。结果表明壳聚糖的失活动力学符合一级反应的失活动力学方程,在考察溶液澄清率（絮凝率）在不同时间、温度下变化规律的基础上推算出失活速率常数、活化能等动力学函数值,为研究絮凝作用中絮凝剂失活的机理提供理论支持。     

Engineering self-flocculating Halomonas campaniensis for wastewaterless open and continuous fermentation

Halomonas has been developed as a platform for the next generation industrial biotechnology allowing open and nonsterile growth without microbial contamination under a high-salt concentration and alkali pH. To reduce downstream cost associated with continuous centrifugation and salt containing wastewater treatment, Halomonas campaniensis strain LS21 was engineered to become self-flocculating by knocking out an etf operon encoding two subunits of an electron transferring flavoprotein in the predicted electron transfer chain. Self-flocculation could be attributed to the decrease of the surface charge and increase of the cellular hydrophobicity resulted from deleted etf. A wastewaterless fermentation strategy based on the self-flocculating H. campaniensis was developed for growth and the production of poly-3-hydroxybutyrate (PHB) as an example. Most microbial cells flocculated and precipitated to the bottom of the bioreactor within 1 min after stopping the aeration and agitation. The supernatant can be used again without sterilization or inoculation for the growth of the next batch after collecting the precipitated cell mass. The wastewaterless process was conducted for four runs without generating wastewater. PHB accumulation by the self-flocculent strain was enhanced via promoter and ribosome binding site optimizations, the productivities of cell dry weight and PHB were increased from 0.45 and 0.18 g·L ⁻¹·hr ⁻¹ for the batch process compared to 0.82 and 0.33 g·L ⁻¹·hr ⁻¹ for the wastewaterless continuous process, respectively. This has clearly demonstrated the advantages of the wastewaterless process in that it not only reduces wastewater but also increases cell growth and product formation efficiency in a given period of time.     

Flocculation increases the efficacy of depth filtration during the downstream processing of recombinant pharmaceutical proteins produced in tobacco

Flocculation is a cost‐effective method that is used to improve the efficiency of clarification by causing dispersed particles to clump together, allowing their removal by sedimentation, centrifugation or filtration. The efficacy of flocculation for any given process depends on the nature and concentration of the particulates in the feed stream, the concentration, charge density and length of the flocculant polymer, the shear rate, the properties of the feed stream (e.g. pH and ionic strength) and the properties of the target products. We tested a range of flocculants and process conditions using a design of experiments approach to identify the most suitable polymers for the clarification step during the production of a HIV‐neutralizing monoclonal antibody (2G12) and a fluorescent marker protein (DsRed) expressed in transgenic tobacco leaves. Among the 23 different flocculants we tested, the greatest reduction in turbidity was achieved with Polymin P, a branched, cationic polyethylenimine with a charge density of 13.0 meq/g. This flocculant reduced turbidity by more than 90% under a wide range of process conditions. We developed a model that predicted its performance under different process conditions, and this enabled us to increase the depth filter capacity three–sevenfold depending on the process scale, depth filter type and plant species. The costs of filter consumables were reduced by more than 50% compared with a process without flocculant, and there was no loss of recovery for either 2G12 or DsRed.     

衔接重复序列对酵母菌絮凝蛋白功能的调控作用

【目的】了解絮凝基因FLO1中重复DNA序列B和D对絮凝蛋白Flo1p功能的影响,为构建遗传稳定的最小絮凝功能基因奠定理论基础。【方法】通过PCR和融合PCR方法分别克隆到完整的絮凝基因FLO1、重复DNA序列B和D分别缺失的衍生基因FLO1b和FLO1d,分析这些基因在非絮凝酵母中表达对细胞絮凝特性的影响。【结果】与完整絮凝基因相比,重复DNA序列B和D分别缺失后对酵母细胞絮凝强度没有明显影响,但不同基因在酵母菌中表达产生的絮凝特性受环境因素,如甘露糖浓度和pH等的影响有明显差异。FLO1中重复DNA序列B和D缺失后,细胞絮凝特性受甘露糖抑制的敏感性降低;同时对环境pH的改变具有更广泛的适应性。【结论】重复DNA序列B和D对絮凝蛋白Flo1p结构和功能具有调控作用,二者缺失后,特别是D缺失后会使絮凝蛋白在极端酸碱环境下更稳定。     

Chromosomal location of Lg-FLO1 in bottom-fermenting yeast and the FLO5 locus of industrial yeast

Aims: To determine the chromosomal location and entire sequence of Lg-FLO1, the expression of which causes the flocculation of bottom-fermenting yeast. Methods and Results: Two cosmid clones carrying DNA from a bottom-fermenting yeast chromosome VIII right-arm end were selected by colony hybridization. Sequencing revealed that the clones contained DNA derived from a Saccharomyces cerevisiae type chromosome VIII and a Saccharomyces bayanus type chromosome VIII, both from bottom-fermenting yeast. Conclusions: Lg-FLO1 is located on the S. cerevisiae type chromosome VIII at the same position as the FLO5 gene of the laboratory yeast S. cerevisiae S288c. The unique chromosome VIII structure of bottom-fermenting yeast is conserved among other related strains. FLO5 and Lg-FLO1 promoter sequences are identical except for the presence of three 42 bp repeats in the latter, which are associated with gene activity. Flocculin genes might have been generated by chromosomal recombination at these repeats. Significance and Impact of the Study: This is the first report of the exact chromosomal location and entire sequence of Lg-FLO1. This information will be useful in the brewing industry for the identification of normal bottom-fermenting yeast. Moreover, variations in the FLO5 locus among strains are thought to reflect yeast evolution.     

利用污泥提取液制备微生物絮凝剂

以污水厂剩余污泥作为培养基原料,经过一系列处理,探索微生物絮凝剂产生菌的最适发酵培养基配方,结果表明,污泥预处理条件以pH 12碱解条件最优,碳氮源产出量最大,补加8 g/L葡萄糖后灭菌,微生物絮凝剂产生菌LLin6可正常产絮,絮凝率达91.55%。该结果为降低微生物絮凝剂的制备成本,并实现污泥的减量化和污泥资源化利用提供了基础。     

优良酿酒酵母(面包酵母)三倍体菌株的选育*

通过初筛、单倍体分离、诱变、原生质体融合及杂交等育种技术选育出一株具有高生物量、耐高糖、强絮凝性能的优良酿酒酵母(面包酵母)三倍体菌株ZLFH-121,其生物量分别为原始亲株BL68、BL92、L77的1.22、1.33与1.83倍;絮凝性能明显优于原始亲株BL68、BL92。并对其培养条件进行了优化研究,结果表明三倍体菌株ZLFH-121能够很好地利用糖蜜培养基,并表现出良好的絮凝能力。在优化的培养条件下,生物量提高至93.82g/L(湿重),为初始培养条件下的1.30倍。经遗传稳定性分析,证明三倍体菌株ZLFH–121遗传稳定,是一株具有潜在应用价值的优良酿酒酵母(面包酵母)菌株。