Applied Microbiology: Theory ＆ Technology

Performance of Bacteria Lysinibacillus and Enterococcus Faecalis to Degrade PA6 Composites

Oumayma Oulidi — 2024-09-02

The current research focuses on applying bio-reinforced composite materials, specifically emphasizing polyamide 6 (PA6), a widely used thermoplastic polymer known for its mechanical strength and versatility. To enhance the environmental sustainability of PA6, various natural reinforcements, including olive pomace powder (OPP), peanut shell powder (PSP), and plaster (PL), have been incorporated. This comprehensive study investigates the biodegradation of PA6 composites reinforced with these materials in the presence of specific bacteria such as Lysinibacillus sp. and Enterococcus faecalis. These bacteria were chosen for their known ability to degrade synthetic polymers. A range of analytical methods were employed to assess the biodegradation process thoroughly. Mass loss measurements provided quantitative data on the extent of polymer degradation. Scanning electron microscopy (SEM) was used to observe the surface morphology and structural changes in the composites, while infrared spectroscopy (IR) offered insights into the chemical modifications occurring during biodegradation. The results of this study reveal significant insights into the biodegradability of PA6 when reinforced with OPP, PSP, and PL. Notably, adding these bio-reinforcements enhanced the degradation rate of PA6, demonstrating their potential as effective agents for reducing the environmental impact of plastic waste. These findings are crucial in addressing the pressing challenges of ecological pollution caused by polymer waste, emphasizing the importance of developing sustainable materials. By providing a deeper understanding of the biodegradation mechanisms of PA6 composites, this research contributes to the advancement of environmentally friendly approaches in the design and utilization of plastic materials, paving the way for innovative solutions in waste management and pollution reduction.

Comparative Study on the Use of Untreated Water of Mahananda River in West Bengal, India and Household Gray Water for Cultivation of Desmodesmus elegans

Simrat Kaur — 2024-10-21

This is the first study that has compared the use of untreated river and household gray water to obtain highdensity cultures of the microalga Desmodesmus elegans under natural sunlight and at room temperatures. Cultivation of microalgae for all downstream applications requires the use of fresh water, inorganic nutrients, light, and energy to maintain optimal temperatures and harvest the biomass. To minimize our environmental footprint in terms of water, nutrients, and energy, untreated wastewater from two different sources were used. The Mahananda River receives unrestricted discharges of pollutants from urban activities, including the free movement of livestock. The household gray water produced from the laundry and kitchen sink consisted of a mixture of detergent, soap, oil, grease, and dirt from legumes, vegetables, and fruits. The gray water sample with high turbidity was filtered through an in-house dualmedia filter made of sand and activated carbon. The filtration process significantly reduced the chemical oxygen demand (COD) of the gray water sample from 1,260 ppm to 546 ppm. Prior to algae cultivation, the initial measurements of pH, total dissolved solids (TDS), COD, phosphate, and ammonium for river and gray water were 7.44 and 8.5, 115 and 141 ppm, 350 and 546 ppm, 0.44 and 2.4 ppm, 2.5 and 1.7 ppm, respectively. The COD reduction of 74.89% and 54.31% in the river and household gray water respectively was achieved. The novelty of this study is that the cultivation of D. elegans was carried out under natural light and temperature conditions.

Isolation and Characterization of Rhizobacteria Screened from Roots of Limnobium laevigatum

Cassandra Teo Ket Ein — 2024-10-25

The quantity of wastewater is increasing globally due to accelerated urbanization, population growth, and economic development. This drives up the demand for methods to resolve the wastewater problem that has been in short supply. Limnobium laevigatum acts as a hyperaccumulator due to the high accumulation of heavy metals found in the roots of L. laevigatum, such as Zn, Cr, Pb, and Ni, thus showing potential for use in wastewater treatment. This study aims to identify the characteristics of rhizobacteria that screened from the roots of L. laevigatum. This study is randomized, in which 50 colonies are randomly selected from the origins of L. laevigatum. The roots of L. laevigatum are cultivated, and the isolation of the rhizobacteria strains is performed. The characterization of the rhizobacteria is determined by gram staining and biochemical testing. The biochemical testing is evaluated to determine the unidentified rhizobacteria species with catalase activity. 58% of the isolates are found in gram-positive, and 42% of them are gramnegative. The sphere-shaped rhizobacteria arrangements are found in single streptococcus and staphylococcus. In contrast, the rod-shaped rhizobacteria arrangements are observed as single, Diplo, and palisades. The biochemical test resulted in 23 colonies, of which 46% were catalase-positive, and 27 colonies, 54% were observed as catalase-negative. In this study, Fourier transform infrared (FTIR) spectroscopy is performed to identify the different characteristic peak values of various functional compounds in the roots of L. laevigatum. It analyzes the prominent peaks at 56.2454 in 696 cm^-1 that showed strong C-Br stretching, indicating the presence of a halo compound, which can efficiently degrade certain specific aromatic compounds present in wastewater. The rhizobacteria play a vital role in wastewater treatment by decomposing organic matter and pollutants into less toxic or non-toxic substances, reducing biological oxygen demand (BOD), and promoting plant growth by the interaction between plant growth-promoting rhizobacteria and the aquatic plants. In short, this study is expected to advocate sustainable and eco-friendly wastewater treatments by using rhizobacteria that screened in the roots of L. laevigatum.

The Effectiveness of Limnobium laevigatum in Inhibiting the Growth of Microbes Found in Lake Water

Teryna Thu Pui Xing — 2024-10-11

Limnobium laevigatum, commonly called Amazon frogbit, belongs to the Hydrocharitaceae family and thrives in freshwater environments with abundant lighting. This perennial herb has a unique characteristic of floating above the water’s surface but can also establish roots in shallow water. Several studies showed that the roots of L. laevigatum have high removal efficiencies of heavy metals in wasted water up to a concentration of 70%, particularly Zn. However, the investigation of L. laevigatum to treat microorganisms in contaminated water still needs to be explored. After serial dilution, a lake water sample was isolated to identify the types of microbes. Gram-staining was applied as a preliminary analysis for further identification of the types of microbes by observing under a compound microscope. Following identification, 6 gram-positive and 4 gram-negative bacteria were tested with different amounts of L. laevigatum powder, 0.1 g, 0.2 g, and 0.3 g using a mass spectrophotometer to determine the effectiveness of inhibiting the growth of selected microbes. Gram-staining revealed that 66% of isolates are categorized as gram-positive bacteria, while 34% are gram-negative. Further observation shows that 75.75% of isolates from gram-positive bacteria are bacillus-shaped, and 24.25% are cocci-shaped among all gram-positive. 0.1 g of powder shows the least effect on inhibiting Gram-positive bacteria growth, whereas 0.3 g of powder shows the most impact on bacteria. Graphs with standard deviation (SD) values were plotted to compare the effectiveness between different concentrations of L. laevigatum and the differences between Gram-positive and Gram-negative bacteria. The antimicrobial properties of L. laevigatum show minimal effect on Gram-negative than Gram-positive bacteria. This research aims to assess the efficacy of L. laevigatum for inhibiting microbes’ growth, offering practical applications for sustainable water treatment, contributing to eco-friendly solutions, and promoting environmental sustainability.

Effect of Lactoferrin Loaded on Chitosan Against Staphylococcus Aureus and Pseudomonas Aeruginosa

Saeed Zibaee — 2024-09-26

The increasing resistance of bacterial strains to antimicrobial compounds presents a significant global health challenge. Staphylococcus aureus and Pseudomonas aeruginosa are two such bacteria that pose substantial risks, particularly in causing infections of the respiratory tract and bacteremia. Chitosan, a non-toxic and biocompatible polymer, has demonstrated inhibitory effects on bacterial growth. Lactoferrin, an iron-binding protein found in milk, exhibits antimicrobial properties. In this study, lactoferrin was purified from camel milk using CM Sephadex C-50 chromatography after removing casein through ion exchange chromatography. The purification process was confirmed using SDS-PAGE and the absence of color with tetramethylbenzidine. Subsequently, purified lactoferrin was loaded onto 1% chitosan using thiamine pyrophosphate (TPP). The successful loading of lactoferrin onto chitosan was verified using Scanning Electron Microscopy (SEM), Zeta Potential, Particle Size Determination, and Fourier Transform Infrared Spectroscopy (FTIR). After evaluating the cytotoxicity of various lactoferrin concentrations loaded on chitosan, the antimicrobial effects of lactoferrin (at concentrations of 300 and 350 μg/mL) loaded on chitosan were assessed using a microassay method. The results demonstrated a significant decrease (P-value < 0.01) in the growth of Staphylococcus aureus and Pseudomonas aeruginosa bacteria compared to the control group when treated with 300 μg/mL of lactoferrin-loaded chitosan. Furthermore, a substantial decrease (P-value < 0.001) was observed with a concentration of 350 μg/mL.

Adaptations of Psychrophilic Microorganism to Low-Temperature Environments

Shalini Purwar — 2024-10-25

Earth’s surface has varied environmental conditions. The cold climate can be a rich source of cold-friendly microorganisms known as psychrophiles. They play an important role in global biogeochemical cycles. However, continuous survival at low temperatures is generally considered inhumane to life but is very good for psychrophilic organisms to survive in these environments. Biochemical and physical management attributed to its innate adaptive ability to withstand the cold and the stresses associated with it. This review focuses on biochemical and physiological adaptations that use psychrophilic microorganisms under adverse conditions