Characterization of a bioflocculant from a newly isolated Vagococcus sp. W31

Screening of microorganisms producing flocculating substances was carried out. A strain secreting a large amount of bioflocculant was isolated from wastewater samples collected from the Little Moon River in Beijing. Based on the morphological properties and 16S rDNA sequence analysis, the isolate (designated W31) was classified as Vagococcus sp. A bioflocculant (named MBFW31) produced by W31 was extracted from the culture broth by ethanol precipitation and purified by gel chromatography. MBFW31 was heat-stable and had strong flocculating activity in a wide range of pH with relatively low dosage requirement. MBFW31 was identified as a polysaccharide with molecular weight over 2×10(6). It contained neutral sugar and uronic acid as its major and minor components, respectively. Infrared spectra showed the presence of hydroxyl, carboxyl and methoxyl group in its molecules. The present results suggested that MBFW31 had potential application in wastewater treatment

Polyhydroxyalkanoate (PHA) bioplastics from organic waste

Polyhydroxyalkanoates (PHA) bioplastics, which are produced by pure and mixed culture biotechnology, are high-performance and truly biodegradable materials. The use of organic wastes as feedstocks for PHA production has been widely documented, though the focus has been on increasing PHA yield; knowledge of the resulting polymer quality and processability has been lacking. In this chapter, it is shown that copolymer composition, blend composition, thermal properties, molecular weight, type of processing and other characteristics such as microstructure and crystallisation kinetics all govern the mechanical properties, but property-structure relationships are complex, and therefore more research in this space is needed, regardless of the feedstock. Still, there is no doubt that organic wastes can be used as feedstocks for PHA production—particularly if they are pretreated—and there is now interest in commercialisation of PHA bioplastics from such wastes. But further advances are tempered with the conclusion that, for organic wastes to be viable feedstocks, the waste must be relatively abundant, concentrated and readily degradable. For some perspective, mass flows of organic wastewater streams from some relevant Australian industries are presented. It is shown that only if all the wastes from any given industry were collected and consolidated would there be sufficient feedstock for production of industrially relevant volumes of PHA

Heavy Metal Removal from Wastewaters by Biosorption: Mechanisms and Modeling

Many industrial activities result in heavy metal dispersion in the environment worldwide. Heavy metals are persistent contaminants, which get into contact with living organisms and humans creating serious environmental disorders. Metals are commonly removed from wastewaters by means of physical-chemical processes, but often microbes are also enrolled to control metal fate. When microorganisms are used as biosorbents for metal entrapment, a process called “biosorption” occurs. Biosorption efficiency is significantly influenced by many parameters such as environmental factors, the sorbing material and the metal species to be removed, and highly depends on whether microbial cultures are alive or dead. Moreover, the presence of biofilm agglomerates is of major importance for metal uptake onto extracellular polymeric substances. In this chapter, the effect of the above mentioned variables on biosorption performance was reviewed. Among the environmental factors, pH rules metal mobility and speciation. Temperature has a lower influence with an optimal value ranging between 20 and 35 °C. The co-presence of more metals usually decreases the biosorption efficiency of each single metal. Biosorption efficiency can be enhanced by using living microorganisms due to the interaction with active functional groups and the occurrence of transport phenomena into the cells. The existing mathematical modeling approaches used for heavy metal biosorption were overviewed. Several isotherms, obtained in batch conditions, are available for modeling biosorption equilibria and kinetics. In continuous systems, most of the models are used to predict the breakthrough curves. However, the modeling of complex continuous-flow reactors requires further research efforts for better incorporating the effect of the operating parameters and hydrodynamics