Efficient production and characterization of homopolymeric poly(3-hydroxyvalerate) produced by Bacillus strain PJC48.

Aliphatic polyester, poly(3-hydroxyvalerate) (PHV), is commonly produced as a granular component in bacterial cells of various species. Based on 16S rDNA gene sequence analysis, strain PJC48 was identified as a Bacillus species. The current study is aimed to screen for a high-yield strain that can produce PHV efficiently and to increase PHV product yield by optimizing the fermentative process. We identified a high-producer strain based on Nile red staining. Characterization of the PHV produced by PJC48 by nuclear magnetic resonance spectroscopy revealed that it consisted of (R)-3-hydroxyvalerate monomers. The suggested model was validated by response surface methodology. Optimization of the PHV yield resulted in an increase of 32.75% compared to control, with a maximum production of 1.64 g/L after 48 H.

Management of biofilm by an innovative layer-structured membrane for membrane biofilm reactor (MBfR) to efficient methane oxidation coupled to denitrification (AME-D).

Aerobic methane oxidation coupled with denitrification (AME-D) has garnered significant attention as a promising technology for nitrogen removal from water. Effective biofilm management on the membrane surface is essential to enhance the efficiency of nitrate removal in AME-D systems. In this study, we introduce a novel and scalable layer-structured membrane (LSM) developed using a meticulously designed polyurethane sponge. The application of the LSM in advanced biofilm management for AME-D resulted in a substantial enhancement of denitrification performance. Our experimental results demonstrated remarkable improvements in nitrate-removal flux (92.8 mmol-N m-2 d-1) and methane-oxidation rate (325.6 mmol m-2 d-1) when using an LSM in a membrane biofilm reactor (L-MBfR) compared with a conventional membrane reactor (C-MBfR). The l-MBfR exhibited 12.4-, 6.8- and 3.4-fold increases in nitrate-removal rate, biomass-retention capacity, and methane-oxidation rate, respectively, relative to the control C-MBfR. Notably, the l-MBfR demonstrated a 3.5-fold higher abundance of denitrifying bacteria, including Xanthomonadaceae, Rhodocyclaceae, and Methylophilaceae. In addition, the denitrification-related enzyme activity was twice as high in the l-MBfR than in the C-MBfR. These findings underscore the LSM's ability to create anoxic/anaerobic microenvironments conducive to biofilm formation and denitrification. Furthermore, the LSM exhibited a unique advantage in shaping microbial community structures and facilitating cross-feeding interactions between denitrifying bacteria and aerobic methanotrophs. The results of this study hold great promise for advancing the application of MBfRs in achieving efficient and reliable nitrate removal through the AME-D pathway, facilitated by effective biofilm management.

Biofilm stratification in counter-diffused membrane biofilm bioreactors (MBfRs) for aerobic methane oxidation coupled to aerobic/anoxic denitrification: Effect of oxygen pressure.

Aerobic methane oxidation coupled with denitrification (AME-D) executed in membrane biofilm bioreactors (MBfRs) provides a high promise for simultaneously mitigating methane (CH4) emissions and removing nitrate in wastewater. However, systematically experimental investigation on how oxygen partial pressure affects the development and characteristics of counter-diffusional biofilm, as well as its spatial stratification profiles, and the cooperative interaction of the biofilm microbes, is still absent. In this study, we combined Optical Coherence Tomography (OCT) with Confocal Laser Scanning Microscopy (CLSM) to in-situ characterize the development of counter-diffusion biofilm in the MBfR for the first time. It was revealed that oxygen partial pressure onto the MBfR was capable of manipulating biofilm thickness and spatial stratification, and then managing the distribution of functional microbes. With the optimized oxygen partial pressure of 5.5 psig (25% oxygen content), the manipulated counter-diffusional biofilm in the AME-D process obtained the highest denitrification efficiency, due mainly to that this biofilm had the proper dynamic balance between the aerobic-layer and anoxic-layer where suitable O2 gradient and sufficient aerobic methanotrophs were achieved in aerobic-layer to favor methane oxidation, and complete O2 depletion and accessible organic sources were kept to avoid constraining denitrification activity in anoxic-layer. By using metagenome analysis and Fluorescence in situ hybridization (FISH) staining, the spatial distribution of the functional microbes within counter-diffused biofilm was successfully evidenced, and Rhodocyclaceae, one typical aerobic denitrifier, was found to survive and gradually enriched in the aerobic layer and played a key role in denitrification aerobically. This in-situ biofilm visualization and characterization evidenced directly for the first time the cooperative path of denitrification for AME-D in the counter-diffused biofilm, which involved aerobic methanotrophs, heterotrophic aerobic denitrifiers, and heterotrophic anoxic denitrifiers.

Simultaneous enhancement of nitrate removal flux and methane utilization efficiency in MBfR for aerobic methane oxidation coupled to denitrification by using an innovative scalable double-layer membrane.

Endevours on the enhancement of nitrate removal efficiency during methane oxidation coupled with denitrification (AME-D) has always overlooked the role of membrane employed. It would be highly beneficial to enrich the biomass content and to manage biofilm on the membrane, in the utilization of methane and denitrification. In this study, an innovative and scalable double-layer membrane (DLM) was designed and prepared for a membrane biofilm reactor (MBfR), to simultaneously enhance nitrate removal flux and methane utilization efficiency during aerobic methane oxidation coupled with the denitrification (AME-D) process. The DLM allowed quick bacterial attachment and biomass accumulation for biofilm growth, which would be then self-regulated for well distribution of functional microbes on/within the DLM. Upon a high biofilm density of over 70 g-VSS m-2 achieved on the DLM, the methane utilization efficiency of the MBfR was enhanced significantly to over 1.3 times than the control MBfR with conventional polypropylene membrane. The MBfR employed DLM also demonstrated the maximum nitrate removal flux of 740 mg-NO3--N m-2 d-1 that was approximately 1.64 times of that in control MBfR at continuous-mode operation. This DLM indeed favored the enrichment of Type II aerobic methanotrophs of Methylocystaceae, and methanol-utilization denitrifiers of Rhodocyclaceae that preferentially utilize methanol as the cross-feeding intermediates to promote the methane utilization efficiency, and thus to enhance the nitrate removal flux. These results raised from new designed DLM confirmed the importance of membrane surface properties on the effectiveness of MBfR, and offered great potential to address challenging problems of MBfRs during engineering application.

Draft Genome Sequence of a Polydroxyalkanoate-Synthesizing Bacterium, Bacillus sp. Strain PJC48, Isolated from Activated Sludge.

The genome sequence of a Bacillus strain is capable of synthesizing polyhydroxyalkanoates, and Bacillus sp. is considered a platform strain for the production of many biodegradable materials. Here, we present the sequence of the PJC48 strain genome, which is composed of three chromatin structures, an extracellular structure, and a cytoskeleton.

[Spatial distribution pattern of Picea schrenkiana var. tianshanica population and its relationships with topographic factors in middle part of Tianshan Mountain].

By the method of point pattern analysis, this paper studied the spatial distribution patterns of different age class individuals in the Picea schrenkiana var. tianshanica forest in middle part of Tianshan Mountain and the influence of topographic factors on the distribution patterns. It was observed that the density of different age class individuals in the forest decreased with the increasing DBH of the individuals, and except old trees which presented a random distribution at the scale of 0-12 m, the saplings and the small, medium, and big trees were in aggregative distribution at all scales. With the increase of age class, the scale at which the individuals presented the highest aggregation degree increased, whereas the aggregation intensity declined. At small scale (0-16 m), different age class individuals appeared negative association, and the greater difference the tree age, the more significant the negative association presented. Altitude had significant positive effects on the number of medium, big, and old trees but had little effects on the number of saplings and small trees. Slope grade had significant positive effects on the number of saplings and small and medium trees, significant negative effects on the number of old trees, but little effects on the number of big trees. Concavo-convex had significant negative effects on the number of saplings and small and medium trees but had little effects on the number of big and old trees.