An accelerated biodegradation of Poly(lactic acid) by inoculation of Pseudomonas geniculate WS3 combined with nutrient addition

Abstract This study aims to develop an efficient method for accelerating the biodegradation rate of Polylactic acid (PLA). A combined use of PLA-degrading bacterium, Pseudomonas geniculate WS3 and nitrogen source or enzyme inducer to accelerate biodegradation of PLA was proposed. PLA films were prepared and submerged in basal salt medium (BSM) amended with ammonium sulfate, soytone, sericin or sodium lactate and inoculated with P. geniculate WS3 for 30 days. The results showed that the highest percentage of PLA film-weight loss was found in the treatment of soytone addition, followed by sodium lactate addition. PLA films in culture broth with P. geniculate WS3 and soytone were cracked and broken down into small fragments within 20 days. In addition, increasing the lactic acid content as a monomer of PLA in culture broth was directly correlated with increasing the percentage of PLA film-weight loss. It could be concluded that a combined use of P. geniculate WS3 and soytone exhibited a high potential to significantly accelerate the PLA biodegradation under the submerged condition.</jats:p

ohrR and ohr Are the Primary Sensor/Regulator and Protective Genes against Organic Hydroperoxide Stress in Agrobacterium tumefaciens

The genes involved in organic hydroperoxide protection in Agrobacterium tumefaciens were functionally evaluated. Gene inactivation studies and functional analyses have identified ohr, encoding a thiol peroxidase, as the gene primarily responsible for organic hydroperoxide protection in A. tumefaciens. An ohr mutant was sensitive to organic hydroperoxide killing and had a reduced capacity to metabolize organic hydroperoxides. ohr is located next to, and is divergently transcribed from, ohrR, encoding a sensor and transcription regulator of organic hydroperoxide stress. Transcription of both ohr and ohrR was induced by exposure to organic hydroperoxides but not by exposure to other oxidants. This induction required functional ohrR. The results of gel mobility shift and DNase I footprinting assays with purified OhrR, combined with in vivo promoter deletion analyses, confirmed that OhrR regulated both ohrR and ohr by binding to a single OhrR binding box that overlapped the ohrR and ohr promoters. ohrR and ohr are both required for the establishment of a novel cumene hydroperoxide-induced adaptive response. Inactivation or overexpression of other Prx family genes (prx1, prx2, prx3, bcp1, and bcp2) did not affect either the resistance to, or the ability to degrade, organic hydroperoxide. Taken together, the results of biochemical, gene regulation and physiological studies support the role of ohrR and ohr as the primary system in sensing and protecting A. tumefaciens from organic hydroperoxide stress

Microbial Inoculants-Assisted Phytoremediation for Sustainable Soil Management.

Agricultural soil Pollution refers to its accumulation of heavy metals and related compounds which could be from natural or anthropogenic sources. This threatens food quality, food security and environmental health. The traditional physico-chemical technologies soil washing used for soil remediation render the land useless as a medium for plant growth, as they remove all biological activities. Others are labour intensive and have high maintenance cost. Phytoremediation, sustainable and cheaper in situ remediation techniques was therefore considered. However plants do not have the capability to degrade many soil pollutants especially the organic pollutant. It is therefore imperative to take advantage of the degrading ability of soil microorganisms. This chapter therefore focuses on phytoremediation techniques augmented by microbial inoculants

Improvement of mechanical-antibacterial performances of AR/PMMA with TiO2 and HPQM treated by N-2(aminoethyl)-3-aminopropyl trimethoxysilane

© The Author(s) 2020. The mechanical and antibacterial properties of acrylic rubber/poly(methyl methacrylate) (AR/PMMA) blend at 10 to 50 wt% of AR content with non-treated and treated titanium dioxide (TiO2) and 2-Hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM) by N-2(aminoethyl)-3-aminopropyl trimethoxysilane were studied. The antibacterial property against Escherichia coli was evaluated. The results found that the mechanical properties of ARt-TiO2/PMMA and ARt-HPQM/PMMA blend were higher than that of the ARTiO2/PMMA and ARHPQM/PMMA blend. For antibacterial property, the ARHPQM/PMMA and ARt-HPQM/PMMA blend could act as the antibacterial material, while the ARTiO2/PMMA blend did not show. However, the ARt-TiO2/PMMA blend could inhibit bacterial cell growth with 10 to 30 wt% of AR content. The recommended compositions of ARt-TiO2/PMMA blend, which improved both mechanical and antibacterial properties, were 10 to 30 wt% of AR and were 10 to 50 wt% of AR for ARt-HPQM/PMMA. Moreover, the UV radiation increased the antibacterial properties by the destruction of the interaction in treated TiO2 and HPQM and improved the antibacterial performance of ARt-TiO2/PMMA and ARt-HPQM/PMMA blend