Enhanced bacterial affinity of PVDF membrane: its application as improved sea water sampling tool for environmental monitoring

Enhanced understanding of nitrogen fixing bacteria through DNA extraction with polyvinylidene fluoride membrane

The rhizobiota, particularly nitrogen-fixing bacteria, play a crucial role in plant functioning by providing essential nutrients and defense against pathogens. This study investigated the diversity of nitrogen-fixing bacteria in a relatively understudied habitat: technosoils developed from industrial soda production. To analyze the bacterial diversity in the rhizosphere soils of wheat (Triticum aestivum L.) and aster (Tripolium pannonicum Jacq.), regions of the nifH gene were amplified and sequenced from the resident bacterial communities. A polyvinylidene fluoride (PVDF) membrane was employed for metagenomic DNA extraction, enhancing the detection of nitrogen-fixing bacteria. Prior to standard DNA extraction, an enrichment step was conducted in nitrogen-free JMV medium at 26 °C for 24 h, with a modification that replaced soil with the PVDF membrane. This approach enabled a more comprehensive analysis of the rhizosphere bacterial community, revealing that unique amplicon sequence variants (ASVs) in aster and wheat membrane samples accounted for a notable proportion of all ASVs in the dataset (8.5% and 23%, respectively) that were not captured using the standard method. Additionally, our findings demonstrated higher alpha diversity of nitrogen-fixing bacteria in the wheat rhizosphere compared to the aster rhizosphere. In wheat, the dominant genus was Insolitispirillum (38.80%), followed by unclassified genera within Gammaproteobacteria (9.76%) and Rhodospirillaceae (4.74%). In contrast, the aster rhizosphere was predominantly occupied by Azotobacter (95.69%).

A novel technique for the preparation of curd (Dahi) by PVDF membrane-based strip

Preparation of curd at home is quite challenging as it requires skills like addition of proper amount of starter culture, maintenance and storage of inoculum for the preparation of good and consistent quality curd. The present work utilized bacterial attachment property of PVDF (Polyvinylidene fluoride) membrane to prepare a strip which can be dipped into milk for the preparation of consistent quality curd. Shelf-life of the strip is around 100 days. The strip prepared curd was well comparable with the curd prepared by the commercial inoculum based on their pH, % lactic acid, % syneresis and bacterial load. Strip of size 5 × 5 cm2 was enough for preparation of 500 mL curd. It was proved by different analytical techniques like AFM, SEM and FTIR that PVDF was not having any leaching property during curd preparation. It can also be used in repeated contact with food products, as it is FDA (Food and Drug Administration) compliant and non-toxic. The curd strip has significant industrial relevance as it is a cost-effective alternative of any commercial inoculum (very expensive) and also meets the demand of consumers with the rising health awareness and busy lifestyles. Further, it is spillage proof, portable, ready-to-use.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-021-05339-3.

In-depth performance study of an innovative decentralized multistage constructed wetland system treating real institutional wastewater

The performance of an innovative decentralized multistage constructed wetland (DMCW) treating institutional wastewater is studied covering three seasons. The DMCW system with Canna lily efficiently removed organics contaminants like COD and BOD, and nutrients from the wastewater, showing its dependency on meteorological factors. Overall the performance is maximum in summer and least in monsoon, with a COD removal of 85.6% in summer followed by 82.5% in winter and 61.2% in monsoon. Removal of TSS (67.7-85.5%), PO₄^3--P (52.1-64.4%), NH₄⁺-N (56.6-71.6%), NO₃^--N (47.3-63.4%) and NO₂^--N (62-75.4%) were achieved along with heavy metals like Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Hg and Pb. Removal of pathogens like Vibrio is >98%, E. coli 95%, Pseudomonas 99%, and Aeromonas 63% was observed. Mass removal rate of COD was maximum in summer (97.3 g/m²/d) followed by winter (78.7 g/m²/d) and monsoon (43.5 g/m²/d). Majority of organics removal during the treatment was highlighted through Gas Chromatography-Mass Spectrometry (GCMS) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed wastewater to be complex. The Canna lily accumulated various elements and oxides during the treatment with no stress on its health. The treated water quality is within the permissible limits and stands suitable for irrigational purposes. Better plant health and increased microbial diversity in the garden proves the suitability of treated water for irrigational activities. The results were validated using statistical tools like Mann-Whitney U test and principal component analysis.

An improved device with an affinity membrane to collect depth specific contamination free water for environmental assessment

The prime requirement for marine water studies is a competent sampling device that can collect water samples perfectly without any contamination to avoid false analysis.