Role of extremophilic Bacillus cereus KH1 and its lipopeptide in treatment of organic pollutant in wastewater

Highly efficient bio-production of putrescine from L-arginine with arginase and L-ornithine decarboxylase in engineered Escherichia coli

To achieve industrial-scale putrescine production, a high efficient bio-synthesis of putrescine involving arginase (ARG, EC 3.5.3.1) and L-ornithine decarboxylase was evaluated here. Among the four arginases tested, ARGBT from Bos Taurus showed the highest activity (1966 U/mg). Compared to the L-arginine decarboxylase (ADC) pathway, the strain expressing ARGBT and L-ornithine decarboxylase (SpeC) produced 28.7 g/L putrescine, a 38.6 % increase. Two pyridoxal phosphate (PLP) salvage pathways were evaluated, and the strain BL-PTac-PdxK co-expressed pyridoxal kinase (PdxK) performed better. D-Glucose was used as the co-substrate to improve the putrescine titer further. Under optimal conditions, 43.6 g/L putrescine was produced from 87.1 g/L L-arginine, and 76 g/L putrescine was synthesized on a 0.5 L scale. Using L-arginine fermentation broth (60 g/L) as the substrate, a titer of 30 g/L putrescine was achieved. This efficient biotransformation process presented here enables feasible industrial-scale putrescine production.

Biosurfactant production by Bacillus cereus GX7 utilizing organic waste and its application in the remediation of hydrocarbon-contaminated environments

The use of biosurfactants represents a promising technology for remediating hydrocarbon pollution in the environment. This study evaluated a highly effective biosurfactant strain-Bacillus cereus GX7's ability to produce biosurfactants from industrial and agriculture organic wastes. Bacillus cereus GX7 showed poor utilization capacity for oil soluble organic waste but effectively utilized of water- soluble organic wastes such as starch hydrolysate and wheat bran juice as carbon sources to enhance biosurfactant production. This led to significant improvements in surface tension and emulsification index. Corn steep liquor was also effective as a nitrogen source for Bacillus cereus GX7 in biosurfactant production. The biosurfactants produced by strain Bacillus cereus GX7 demonstrated a remediation effect on oily beach sand, but are slightly inferior to chemical surfactants. Inoculation with Bacillus cereus GX7 (70.36%) or its fermentation solution (94.38%) effectively enhanced the degradation efficiency of diesel oil in polluted seawater, surpassing that of indigenous degrading bacteria treatments (57.62%). Moreover, inoculation with Bacillus cereus GX7's fermentation solution notably improved the community structure by increasing the abundance of functional bacteria such as Pseudomonas and Stenotrophomonas in seawater. These findings suggest that the Bacillus cereus GX7 as a promising candidate for bioremediation of petroleum hydrocarbons.

Applications of Fourier Transform-Infrared spectroscopy in microbial cell biology and environmental microbiology: advances, challenges, and future perspectives

Microorganisms play pivotal roles in shaping ecosystems and biogeochemical cycles. Their intricate interactions involve complex biochemical processes. Fourier Transform-Infrared (FT-IR) spectroscopy is a powerful tool for monitoring these interactions, revealing microorganism composition and responses to the environment. This review explores the diversity of applications of FT-IR spectroscopy within the field of microbiology, highlighting its specific utility in microbial cell biology and environmental microbiology. It emphasizes key applications such as microbial identification, process monitoring, cell wall analysis, biofilm examination, stress response assessment, and environmental interaction investigation, showcasing the crucial role of FT-IR in advancing our understanding of microbial systems. Furthermore, we address challenges including sample complexity, data interpretation nuances, and the need for integration with complementary techniques. Future prospects for FT-IR in environmental microbiology include a wide range of transformative applications and advancements. These include the development of comprehensive and standardized FT-IR libraries for precise microbial identification, the integration of advanced analytical techniques, the adoption of high-throughput and single-cell analysis, real-time environmental monitoring using portable FT-IR systems and the incorporation of FT-IR data into ecological modeling for predictive insights into microbial responses to environmental changes. These innovative avenues promise to significantly advance our understanding of microorganisms and their complex interactions within various ecosystems.

Water lettuce (Pistia stratiotes L.) increases biogas effluent pollutant removal efficacy and proves a positive substrate for renewable energy production

Background

Aquatic plants play a crucial role in nature-based wastewater treatment and provide a promising substrate for renewable energy production using anaerobic digestion (AD) technology. This study aimed to examine the contaminant removal from AD effluent by water lettuce (WL) and produce biogas from WL biomass co-digested with pig dung (PD) in a farm-scale biogas digester.

Methods

The first experiment used styrofoam boxes containing husbandry AD effluent. WLs were initially arranged in 50%, 25%, 12.5%, and 0% surface coverage. Each treatment was conducted in five replicates under natural conditions. In the second experiment, WL biomass was co-digested with PD into an existing anaerobic digester to examine biogas production on a farm scale.

Results

Over 30 days, the treatment efficiency of TSS, BOD5, COD, TKN, and TP in the effluent was 93.75-97.66%, 76.63-82.56%, 76.78-82.89%, 61.75-63.75%, and 89.00-89.57%, respectively. Higher WL coverage increased the pollutant elimination potential. The WL biomass doubled after 12 days for all treatments. In the farm-scale biogas production, the biogas yield varied between 190.6 and 292.9 L kg VSadded-1. The methane content reached over 54%.

Conclusions

WL removed AD effluent nutrients effectively through a phytoremediation system and generated significant biomass for renewable energy production in a farm-scale model.

Immobilization of Subtilisin Carlsberg and its use for transesterification of N-acetyl-L-phenylalanine ethyl ester in organic medium

In this study, inorganic-based carrier perlite (PER) and cyclodextrin-modified perlite (PER-CD) were used for Subtilisin Carlsberg (SC) immobilization. For enzyme immobilization, the supports aminated with 3-aminotriethoxysilane were first activated with glutaraldehyde (GA) and genipin (GE), and then, the immobilized enzymes (PER-SC and PER-CD-SC) were obtained. The reaction medium for SC immobilization consisted of 500 mg carrier and 5 ml (1 mg/ml) enzyme solution. The immobilization conditions were pH 8.0, 25 °C, and 2 h incubation time. Free and immobilized SC were used for transesterification of N-acetyl-L-phenylalanine ethyl ester (APEE) with 1-propanol in tetrahydrofuran (THF). The transesterification activity of the enzyme and the yield of the transesterification reaction were determined by gas chromatography (GC). 50 mg of immobilized or 2.5 mg of free SC was added to the reaction medium, which was prepared as 1 mmol APEE and 10 mmol alcohol in 10 mL of THF. The conditions for the transesterification reaction were 60 °C and 24 h of incubation. The structure and surface morphology of the prepared carriers were characterized using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Casein substrate was used in the optimization study. The optimum temperature and pH for SC activity were found to be 50 °C and pH 8.0, respectively, for free and immobilized SC. The thermal stability of immobilized SC was found to be greater than that of free SC. At the end of 4 h of exposure to high temperature, the immobilized enzyme maintained its activity at approximately 50%, while the free enzyme was maintained at approximately 20%. However, modification with cyclodextrin did not alter the thermal stability. The transesterification yield was found to be approximately 55% for the free enzyme, while it was found to be approximately 68% and 77% for PER-SC and PER-CD-SC, respectively. The effect of metal ions and salts on transesterification yield was examined. The results showed that the addition of metal ions decreased the percentage of transesterification by approximately 10% compared to the control group, whereas the addition of salt significantly decreased the percentage of transesterification by 60-80% compared to the control group.

Biodegradation mechanism of chlorpyrifos by halophilic bacterium Hortaea sp. B15

For decades, most of the developing nations have relied on chlorpyrifos for insecticidal activity in the agriculture sector. It is a common chlorinated organophosphorus pesticide that has been widely used to control insects to protect plants. This study aimed to investigate the effects of environmental characteristics such as salinity, pH, temperature, and surfactant on Hortaea sp. B15 mediated degradation of chlorpyrifos as well as enzyme activity and metabolic pathway. The highest bacterial growth (4.6 × 10¹⁶ CFU/mL) was achieved after 20 h of incubation in a 100 mg/L chlorpyrifos amended culture. The fit model and feasible way to express the chlorpyrifos biodegradation kinetics in normal condition and optimized was a first-order rate equation, with an R² value of 0.95-0.98. The optimum pH for chlorpyrifos biodegradation was pH 9, which resulted in a high removal rate (91.1%) and a maximum total count of 3.8 × 10¹⁶ CFU/mL. Increasing the temperature over 40 °C may inhibit microbial development and biodegradation. There was no significant effect of culture salinity on degradation and bacterial growth. In the presence of non-ionic surfactant Tween 80, the maximum chlorpyrifos degradation (89.5%) and bacterial growth (3.8 × 10¹⁶ CFU/mL) was achieved. Metabolites such as 3,5,6-trichloropyridin-2-ol and 2-pyridinol were identified in the Hortaea sp. B15 mediated degradation of chlorpyrifos. According to the findings, Hortaea sp. B15 should be recommended for use in the investigation of in situ biodegradation of pesticides.

Gut microbiota-mitochondrial inter-talk in non-alcoholic fatty liver disease

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD), which is a progressive disease, has exerted huge a healthcare burden worldwide. New investigations have suggested that the gut microbiota closely participates in the progression of NAFLD through the gut-liver axis or gut-brain-liver axis. The composition of the microbiota can be altered by multiple factors, primarily dietary style, nutritional supplements, or exercise. Recent evidence has revealed that gut microbiota is involved in mitochondrial biogenesis and energy metabolism in the liver by regulating crucial transcription factors, enzymes, or genes. Moreover, microbiota metabolites can also affect mitochondrial oxidative stress function and swallow formation, subsequently controlling the inflammatory response and regulating the levels of inflammatory cytokines, which are the predominant regulators of NAFLD. This review focuses on the changes in the composition of the gut microbiota and metabolites as well as the cross-talk between gut microbiota and mitochondrial function. We thus aim to comprehensively explore the potential mechanisms of gut microbiota in NAFLD and potential therapeutic strategies targeting NAFLD management.