Insights from comparative proteomic analysis into degradation of phenanthrene and salt tolerance by the halophilic Martelella strain AD-3

Unraveling the mechanisms of benzo[a]pyrene degradation by Pigmentiphaga kullae strain KIT-003 using a multi-omics approach

Polycyclic aromatic hydrocarbons (PAHs), notably benzo[a]pyrene (BaP), are environmental contaminants with multiple adverse ecological implications. Numerous studies have suggested the use of BaP biodegradation using various bacterial strains to remove BaP from the environment. This study investigates the BaP biodegradation capability of Pigmentiphaga kullae strain KIT-003, isolated from the Nak-dong River (South Korea) under specific environmental conditions. The optimum conditions of biodegradation were found to be pH 7.0, 35°C, and a salinity of 0 %. GC-MS analysis suggested alternative pathways by which KIT-003 produced catechol from BaP through several intermediate metabolites, including 4-formylchrysene-5-carboxylic acid, 5,6-dihydro-5,6-dihydroxychrysene-5-carboxylic acid (isomer: 3,4-dihydro-3,4-dihydroxychrysene-4-carboxylic acid), naphthalene-1,2-dicarboxylic acid, and 2-hydroxy-1-naphthoic acid. Proteomic profiles indicated upregulation of enzymes associated with aromatic compound degradation, such as nahAc and nahB, and of those integral to the tricarboxylic acid cycle, reflecting the strain's adaptability to and degradation of BaP. Lipidomic analysis of KIT-003 demonstrated that BaP exposure induced an accumulation of glycerolipids such as diacylglycerol and triacylglycerol, indicating their crucial role in bacterial adaptation mechanisms under BaP stress. This study provides significant scientific knowledge regarding the intricate mechanisms involved in BaP degradation by microorganisms.

Microbial-derived salt-tolerant proteases and their applications in high-salt traditional soybean fermented foods: a review

Different microorganisms can produce different proteases, which can adapt to different industrial requirements such as pH, temperature, and pressure. Salt-tolerant proteases (STPs) from microorganisms exhibit higher salt tolerance, wider adaptability, and more efficient catalytic ability under extreme conditions compared to conventional proteases. These unique enzymes hold great promise for applications in various industries including food, medicine, environmental protection, agriculture, detergents, dyes, and others. Scientific studies on microbial-derived STPs have been widely reported, but there has been little systematic review of microbial-derived STPs and their application in high-salt conventional soybean fermentable foods. This review presents the STP-producing microbial species and their selection methods, and summarizes and analyzes the salt tolerance mechanisms of the microorganisms. It also outlines various techniques for the isolation and purification of STPs from microorganisms and discusses the salt tolerance mechanisms of STPs. Furthermore, this review demonstrates the contribution of modern biotechnology in the screening of novel microbial-derived STPs and their improvement in salt tolerance. It highlights the potential applications and commercial value of salt-tolerant microorganisms and STPs in high-salt traditional soy fermented foods. The review ends with concluding remarks on the challenges and future directions for microbial-derived STPs. This review provides valuable insights into the separation, purification, performance enhancement, and application of microbial-derived STPs in traditional fermented foods.

Bioremediation of phenanthrene in saline-alkali soil by biochar- immobilized moderately halophilic bacteria combined with Suaeda salsa L

Polycyclic aromatic hydrocarbon (PAH) contaminated saline-alkali soil is commonly salinized and hardened, which leads to low self-purification efficiency, making it difficult to reuse and remediate. In this study, pot experiments were conducted to investigate remediation of PAH contaminated saline-alkali soil using biochar-immobilized Martelella sp. AD-3, and Suaeda salsa L (S. salsa). Reduction in phenanthrene concentration, PAH degradation functional genes, and the microbial community in the soil were analyzed. The soil properties and plant growth parameters were also analyzed. After a 40-day remediation, the removal rate of phenanthrene by biochar-immobilized bacteria combined with S. salsa (MBP group) was 91.67 %. Additionally, soil pH and electrical conductivity (EC) reduced by 0.15 and 1.78 ds/m, respectively. The fresh weight and leaf pigment contents increased by 1.30 and 1.35 times, respectively, which effectively alleviated the growth pressure on S. salsa in PAH-contaminated saline-alkali soil. Furthermore, this remediation resulted in abundance of PAH degradation functional genes in the soil, with a value of 2.01 × 10³ copies/g. The abundance of other PAH degraders such as Halomonas, Marinobacter, and Methylophaga in soil also increased. Furthermore, the highest abundance of Martelella genus was observed after the MBP treatment, indicating that strain AD-3 has a higher survival ability in the rhizosphere of S. salsa under the protection of biochar. This study provides a green, low-cost technique for remediation of PAH-contaminated saline-alkali soils.

Biological machinery for polycyclic aromatic hydrocarbons degradation: A review

Polycyclic aromatic hydrocarbons (PAHs) are hazardous environmental pollutants with widespread and well-recognized health concerns. Amidst more than a hundred known PAHs, 16 are categorized as priority pollutants. Use of widely diverse biological machinery comprising bacteria, fungi, and algae harnessed from contaminated sites has emerged as an ecologically safe and sustainable approach for PAH degradation. The potential of these biological systems has been thoroughly examined to maximize the degradation of specific PAHs by understanding their detailed biochemical pathways, enzymatic system, and gene organization. Recent advancements in microbial genetic engineering and metabolomics using modern analytical tools have facilitated the bioremediation of such xenobiotics. This review explores the role of microbes, their biochemical pathways, genetic regulation of metabolic pathways, and the effect of biosurfactants against the backdrop of PAH substrate structures.

Biodegradation of aromatic pollutants meets synthetic biology

Ubiquitously distributed microorganisms are natural decomposers of environmental pollutants. However, because of continuous generation of novel recalcitrant pollutants due to human activities, it is difficult, if not impossible, for microbes to acquire novel degradation mechanisms through natural evolution. Synthetic biology provides tools to engineer, transform or even re-synthesize an organism purposefully, accelerating transition from unable to able, inefficient to efficient degradation of given pollutants, and therefore, providing new solutions for environmental bioremediation. In this review, we described the pipeline to build chassis cells for the treatment of aromatic pollutants, and presented a proposal to design microbes with emphasis on the strategies applied to modify the target organism at different level. Finally, we discussed challenges and opportunities for future research in this field.