Advances of enzymes related to microbial cement / 生物工程学报

Microbial induced calcium carbonate precipitation (MICP) refers to the natural biological process of calcium carbonate precipitation induced by microbial metabolism in its surrounding environment. Based on the principles of MICP, microbial cement has been developed and has received widespread attention in the field of biology, civil engineering, and environment owing to the merits of environmental friendliness and economic competence. Urease and carbonic anhydrase are the key enzymes closely related to microbial cement. This review summarizes the genes, protein structures, regulatory mechanisms, engineering strains and mutual synergistic relationship of these two enzymes. The application of bioinformatics and synthetic biology is expected to develop biocement with a wide range of environmental adaptability and high performance, and will bring the MICP research to a new height.

Microbial-induced remediation of Zn2+ pollution based on the capture and utilization of carbon dioxide

Background: Microbial-induced remediation of Zn2+ pollution based on the capture and utilization of carbon dioxide was investigated. In this study, carbon dioxide was absorbed and transformed into carbonate ions under the enzymatic action of Paenibacillus mucilaginosus, which was being utilized to mineralize Zn2+. Results: The compositional and morphological properties of the precipitations were studied using Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The thermal properties of the precipitates were investigated by thermogravimetric-differential scanning calorimetry (TG-DSC). The FTIR results confirmed that the functional groups of the precipitates were CO3² − and OH−. The XRD and EDS patterns showed that basic zinc carbonate could be obtained successfully by Microbial-induced remediation. The SEM micrographs demonstrated that the precipitates were in the nanometer range with sizes of 100-200 nm and were sphere-like in shape. Conclusions: The TG-DSC results showed that weight loss of the precipitates occurred around 253°C. The FTIR and TG-DSC results were in accord with the XRD and EDS results and proved again that the precipitates were basic zinc carbonate. This work thus demonstrates a new method for processing Zn2+ pollution based on the utilization of carbon dioxide.

Ureolytic bacteria isolated from Sarawak limestone caves show high urease enzyme activity comparable to that of Sporosarcina pasteurii (DSM 33)

Aims: Microbial induced calcite precipitation (MICP) is a natural occurring biological process that employs the usage of ureolytic bacteria for a wide range of applications such as improving the mechanical properties of soils. The aim of this study was to isolate and identify local urease-producing bacteria from the limestone caves of Sarawak and characterise their specific urease activities. Methodology and results: Enrichment culture technique was used to isolate urease-producing bacteria. These local isolates were identified using phenotypic and molecular characterisation. Conductivity method and biomass (OD600) measurements were conducted to analyze and determine the specific urease activities of the local isolates. 16S rRNA gene sequence analysis identified the bacterial isolates as Sporosarcina pasteurii, Sporosarcina luteola and Bacillus lentus. Conclusion, significance and impact of study: This is the first study reporting the isolation and identification of urease-producing bacteria from Fairy and Wind Caves situated in Bau, Sarawak, Malaysia. The findings in this study suggest the bacterial isolates are capable of inducing calcite precipitation and serve as alternative microbial ureolytic agents.

Characterization in the archaeological excavation site of heterotrophic bacteria and fungi of deteriorated wall painting of Herculaneum in Italy.

Microbiological characterization of frescos in four different locations (Collegio degli Augustali, Casa del Colonnato Tuscanico, Casa dello Scheletro and Casa del Gran Portale) of excavation sites of Herculaneum was carried out. The use of infrared thermography allowed detecting sample points on frescos with greatest moisture not visible to the naked eye, resulting in structural damage. The microclimatic conditions provided perfect habitat for bacteria and fungi, particularly of spore forming and mould. In fact, heterotrophic bacteria were prevalent in all wall paintings monitored (ranging from 18 ± 2 CFU 100 cm-2 to 68 ± 4 CFU 100 cm-2), whereas fungi were also detected but at lower levels (ranging from 9 ± 2 CFU 100 cm-2 to 45 ± 3 CFU 100 cm-2). Cultural–based method allow us to identify by 16S and 26S rRNA partial sequence analysis heterotrophic microorganisms belonging to different genera of Bacillus and Aspergillus, Penicillium and Fusarium together with the unusual genera as Microascus and Coprinus. By using this approach, Bacillus-related species (B. cereus/B. thuringiensis group, B. simplex/B.muralis group, B. megaterium and B. subtilis) were isolated in all sample points analysed with the exception of the Casa dello Scheletro in which Micrococcus luteus/Arthrobacter sp. group and Streptomyces fragilis were found. DGGE analysis of PCR amplified V3 region of rDNA from DNA directly recovered from frescos samples, enabled identification of bacterial species not identified using culturable technology as those closest related to Microbacterium group, often associated with Brevibacterium, Streptomyces and Stenotrophomonas. Combination of culture-dependent and independent methods provided better microbiology characterization of heterotrophic microbiota present on the surface of ancient frescos of this important archaeological site.