Effects of Water Hardness on Textile Detergency Performance in Aqueous Cleaning Systems

Synthesis of Asymmetric Ionic Hybrid Detergents enables Micelles with Scalable Properties including Cell Compatibility

Ionic detergents enable applications and cause harm in biospheres due to cell toxicity. The utility of covalent combinations between ionic and non-ionic detergent headgroups in modulating cell toxicity remains speculative due to the yet rarely explored synthesis. We close this gap and establish the modular synthesis of ionic/non-ionic hybrid detergents. We restructure a combinatorial methallyl dichloride one-pot coupling into a two-step coupling, which reduces by-products, improves product yields, and enables the gram-scale preparation of asymmetric, cationic/non-ionic and anionic/non-ionic hybrid detergents. Our modular synthesis delivers new modalities for the design of ionic detergents, including an unprecedented scaling of properties that determine applications, such as charge, critical micelle concentration, solubilizing properties, hard water tolerance, and cell compatibility. We uncover that shielding the charge in ionic headgroups can switch the detergent species that is toxic to cells from monomers to mixtures of monomers and micellar assemblies. Establishing the chemistry of ionic/non-ionic hybrid detergents provides a missing evolutionary link in the structural comparison of ionic and non-ionic detergents, enables an easy synthesis access to yet unexplored chemical spaces of asymmetric hybrid materials, and delivers new modalities for designing the toxicity of supramolecular nanomaterials.

Groundwater Quality Assessment in Urban Areas of Malawi: A Case of Area 25 in Lilongwe

Groundwater sources provide an important supply of alternative drinking water in most urban areas in Malawi. This study was conducted to assess the quality of groundwater in Area 25, a typical urban residential area in Malawi. Samples were collected from wells and analyzed for physicochemical and bacteriological parameters following standard methods. Results were compared to Malawi Standards (MS) and World Health Organization (WHO) drinking water quality guidelines. The overall water quality index was computed to ascertain the general quality of the water. Levels of pH, phosphate, sulfate, arsenic, lead, and potassium were below the guideline limits while, electrical conductivity, total dissolved solids, chloride, fluoride, nitrate, total hardness, calcium, and magnesium were observed above permissible limits, posing a health risk to the residents. The quality index ranged from 22 (excellent quality) to 64 (Poor quality) with an average of 41 (good quality). Fecal coliforms were present in 70% of the sampled locations with an average of 7.9 cfu/100 ml. The presence of these bacteria presents a serious risk for waterborne disease outbreaks. This study, therefore, recommends the provision of basic treatment techniques to improve the quality of water in the area before consumption, regular monitoring of groundwater resources, and proper design and setting of septic systems.

Potential of bacteriophages as disinfectants to control of Staphylococcus aureus biofilms

Background

Staphylococcus aureus is the causative agent of chronic mastitis, and can form a biofilm that is difficult to completely remove once formed. Disinfectants are effective against S. aureus, but their activity is easily affected by environmental factors and they are corrosive to equipment and chemically toxic to livestock and humans. Therefore, we investigated the potential utility of a bacteriophage as a narrow-spectrum disinfectant against biofilms formed by S. aureus. In this study, we isolated and characterized bacteriophage vB_SauM_SDQ (abbreviated to SDQ) to determine its efficacy in removing S. aureus biofilms.

Results

SDQ belongs to the family Myoviridae and consists of a hexagonal head, long neck, and short tail. This phage can sterilize a 10⁹ CFU/mL culture of S. aureus in 12 h and multiply itself 1000-fold in that time. Biofilms formed on polystyrene, milk, and mammary-gland tissue were significantly reduced after SDQ treatment. Fluorescence microscopy and scanning electron microscopy showed that SDQ destroyed the biofilm structure. Moreover, the titer of SDQ remained relatively high after the lysis of the bacteria and the removal of the biofilm, exerting a continuous bacteriostatic effect. SDQ also retained its full activity under conditions that mimic common environments, i.e., in the presence of nonionic detergents, tap water, or organic materials. A nonionic detergent (Triton X-100) enhanced the removal of biofilm by SDQ.

Conclusions

Our results suggest that SDQ, a specific lytic S. aureus phage, can be used to control biofilm infections. SDQ maintains its full activity in the presence of nonionic detergents, tap water, metal chelators, and organic materials, and can be used in combination with detergents. We propose this phage as a narrow-spectrum disinfectant against S. aureus, to augment or supplement the use of broad-spectrum disinfectants in the prevention and control of the mastitis and dairy industry contamination caused by S. aureus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02117-1.

Foaming and Cleaning Performance Comparison of Liquid Detergent Formulations using Mixtures of Anionic and Nonionic Surfactants

Modern detergents are typically appreciated for their cleaning performance rather than foaming characteristics. The aim of the current study was to compare the foaming and cleaning abilities of liquid detergents, built from a combination of surfactants, to be applied for household laundry purpose. A total of eighteen different liquid detergent formulations containing mixtures of important anionic, nonionic surfactants, and other additives were prepared. The first set of nine new detergent formulations (S1) was prepared using the surfactants sodium lauryl sulfate (SLS), Tween-20 and Tween-80. Another set of nine new detergent formulations (S2) was prepared using surfactants SLS, Triton X-100 and alkyl polyglucoside (APG). The impact of water quality (RO, hypersaline or hard water) on the foam properties of the detergent formulation sets (S1 and S2) was systematically examined. The second set of detergent formulations (S2) showed a better performance in terms of foamability and foam stability, regardless of the water quality. Also, the surface tension of the detergent formulation set S2 was found to be lower and it showed a higher detergency for both cotton and woolen fabrics. The detergency of the formulation no S2.9 (in set S2) was the maximum amongst all the detergent formulations. The surface morphology of the cotton and woolen fabrics, washed with liquid detergent formulation no S2.9, displayed the removal of oily soil and grease from the surface of the fabrics, without affecting the quality of the fabrics.

Effect of Washing Conditions on Cleaning Action of Linear Alkylbenzene Sulfonate in Hard Water

The effects of water hardness on textile detergency in aqueous linear dodecylbenzene sulfonate (LAS) solutions were examined under various washing conditions. Plain-woven and towel cotton fabrics and plain-woven polyester fabric were soiled with a mixture of carbon black/oleic acid. The soiled fabrics were shake-washed in the LAS solution together with the original unsoiled fabrics. Surface reflectance measurements revealed that the soil removal and redeposition decreased and increased, respectively, with increasing water hardness. The identity of the mineral species (calcium or magnesium ions) in the hard water had no notable effect on the detergency. The addition of significant amounts of extra LAS did not fully compensate the reduction in detergency in hard water. Addition of softening agents and an alkali builder to the hard water limited the reduction in detergency, but the detergency was still lower than that in the absence of hardness salts. Moreover, a high wash temperature and repeated rinse procedure did not prevent the reduction in detergency in hard water. Finally, a washing test was carried out in hard water under the conditions considered to be effective for improving the detergent quality in hard water, based on the experimental results. The LAS detergency toward the cotton fabrics under these conditions was still poorer than that in the absence of hardness salts. We concluded that using soft wash water is the best choice for maximizing the cleaning power of detergents.