Characterization and bioremediation potential of marine Psychrobacter species

Recovery of Y(III) from wastewater by Pseudomonas psychrotolerans isolated from a mine soil

While microbial technologies, which are considered to be environmentally friendly, have great potential for the recovery of rare earth elements (REEs) from mining wastewater, their applications have been restricted due to a lack of efficient biosorbents. In this study, a strain of Pseudomonas psychrotolerans isolated from yttrium-enriched mine soil was used to recover yttrium (Y(III)) from rare-earth mining wastewater. At an initial Y(III) dose of 50 mg L-1, the amount of Y(III) adsorbed by P. psychrotolerans reached 99.9 % after 24 h. Various characterization techniques revealed that P. psychrotolerans adsorbed Y(III) mainly through complexation of oxygen-containing functional groups and electrostatic interactions. A high level of adsorption efficiency (>99.9 %) was maintained after five consecutive adsorption/desorption cycles, indicating that P. psychrotolerans was highly reusable. While the efficiency of adsorbing Y(III) by P. psychrotolerans decreased (34.4 %) in actual rare earth mining wastewater, selectivity toward other REEs (≤ 18.4 %) was still observed. Consequently, this study provides a promising green, environmentally friendly and sustainable microbial approach for the selective recovery of REEs from rare earth wastewater.

Investigating Bio-Inspired Degradation of Toxic Dyes Using Potential Multi-Enzyme Producing Extremophiles

Biological treatment methods overcome many of the drawbacks of physicochemical strategies and play a significant role in removing dye contamination for environmental sustainability. Numerous microorganisms have been investigated as promising dye-degrading candidates because of their high metabolic potential. However, few can be applied on a large scale because of the extremely harsh conditions in effluents polluted with multiple dyes, such as alkaline pH, high salinity/heavy metals/dye concentration, high temperature, and oxidative stress. Therefore, extremophilic microorganisms offer enormous opportunities for practical biodegradation processes as they are naturally adapted to multi-stress conditions due to the special structure of their cell wall, capsule, S-layer proteins, extracellular polymer substances (EPS), and siderophores structural and functional properties such as poly-enzymes produced. This review provides scientific information for a broader understanding of general dyes, their toxicity, and their harmful effects. The advantages and disadvantages of physicochemical methods are also highlighted and compared to those of microbial strategies. New techniques and methodologies used in recent studies are briefly summarized and discussed. In particular, this study addresses the key adaptation mechanisms, whole-cell, enzymatic degradation, and non-enzymatic pathways in aerobic, anaerobic, and combination conditions of extremophiles in dye degradation and decolorization. Furthermore, they have special metabolic pathways and protein frameworks that contribute significantly to the complete mineralization and decolorization of the dye when all functions are turned on. The high potential efficiency of microbial degradation by unculturable and multi-enzyme-producing extremophiles remains a question that needs to be answered in practical research.

Perchlorate-reducing bacteria from Antarctic marine sediments

Perchlorate is a contaminant that can persist in groundwater and soil, and is frequently detected in different ecosystems at concentrations relevant to human health. This study isolated and characterised halotolerant bacteria that can potentially perform perchlorate reduction. Bacterial microorganisms were isolated from marine sediments on Deception, Horseshoe and Half Moon Islands of Antarctica. The results of the 16S ribosomal RNA (rRNA) gene sequence analysis indicated that the isolates were phylogenetically related to Psychrobacter cryohalolentis, Psychrobacter urativorans, Idiomarina loihiensis, Psychrobacter nivimaris, Sporosarcina aquimarina and Pseudomonas lactis. The isolates grew at a sodium chloride concentration of up to 30% and a perchlorate concentration of up to 10,000 mg/L, which showed their ability to survive in saline conditions and high perchlorate concentrations. Between 21.6 and 40% of perchlorate was degraded by the isolated bacteria. P. cryohalolentis and P. urativorans degraded 30.3% and 32.6% of perchlorate, respectively. I. loihiensis degraded 40% of perchlorate, and P. nivimaris, S. aquimarina and P. lactis degraded 22%, 21.8% and 21.6% of perchlorate, respectively. I. loihiensis had the highest reduction in perchlorate, whereas P. lactis had the lowest reduction. This study is significant as it is the first finding of P. cryohalolentis and. P. lactis on the Antarctic continent. In conclusion, these bacteria isolated from marine sediments on Antarctica offer promising resources for the bioremediation of perchlorate contamination due to their ability to degrade perchlorate, showing their potential use as a biological system to reduce perchlorate in high-salinity ecosystems.

Dynamic changes of the bacterial communities in roast chicken stored under normal and modified atmosphere packaging

This study systematically investigated the dynamic changes in bacterial communities in roast chicken in normal and modified atmosphere packaging (MAP). The samples were stored under normal atmosphere and 40%/60% CO₂ /N₂ MAP conditions for 28 days at 4 °C. Changes in the number and type of microorganisms in roast chicken during storage were defined via cultural and 16S rDNA sequencing techniques. More Bacteroides, Chryseobacterium, Lactobacillus, and Acinetobacter than other bacteria were initially found in roast chicken. With normal packaging, Pseudomonas rapidly multiplied and became the main spoilage organism in roast chicken after 7 days, with a relative abundance of >90% of the entire bacterial flora. With MAP, due to the high salt content, Halomonas became the main spoilage organism in roast chicken by the middle of the storage period (14 days). Between days 21 and 28 of storage, Pseudomonas gradually became the main spoilage organism in roast chicken, but its relative abundance was much lower in MAP than in normal packaging, followed by Lachnospiraceae (NK4A136 group) and Altererythrobacter. Our research shows that the microbes in roast chicken mainly originated from the processing environment and operators. The combination of MAP with a low storage temperature could effectively improve the quality and safety of roast chicken meat. PRACTICAL APPLICATIONS: This research showed the dynamic changes in the bacterial community of roast chicken stored under normal and modified atmosphere packaging (MAP). Microorganisms in roast chicken are mainly obtained from the processing environment and operators. Combining MAP with storage at low temperatures can effectively improve the quality and safety of roast chicken.