Research

11 pages, 3241 KiB

Open AccessArticle

Differential Expression of Antioxidant Enzymes in Chlorine-Resistant Acinetobacter and Serratia spp. Isolated from Water Distribution Sites in Mumbai: A Study on Mechanisms of Chlorine Resistance for Sustainable Water Treatment Strategies

by Santosh Jathar, Sanabil Dakhni, Disha Shinde, Abigail Fernandes, Pamela Jha, Neetin Desai, Tareeka Sonawane and Renitta Jobby

Sustainability 2023, 15(10), 8287; https://0-doi-org.brum.beds.ac.uk/10.3390/su15108287 - 19 May 2023

Viewed by 1236

Abstract

Chlorination is a widely used process for disinfecting drinking water, but the emergence of chlorine-resistant bacteria has become a significant concern. While previous research has focused on identifying chlorine-resistant organisms, there has been limited investigation into the mechanisms behind chlorine resistance. Some bacterial [...] Read more.

Chlorination is a widely used process for disinfecting drinking water, but the emergence of chlorine-resistant bacteria has become a significant concern. While previous research has focused on identifying chlorine-resistant organisms, there has been limited investigation into the mechanisms behind chlorine resistance. Some bacterial isolates that display resistance to chlorine treatment may protect themselves using various mechanisms, including biofilm production, antibiotic resistance, horizontal transfer of antibiotic resistance genes, or producing antioxidant enzymes. Given that chlorination employs hypochlorous acid (HOCl), which is an extremely potent oxidizing agent, the most critical mechanism to investigate is antioxidant enzymes. This study investigated the antioxidant profile of eight chlorine-resistant isolates (three of the Serratia sp. and five of the Acinetobacter) after chlorine exposure. The profiles, both between and within species, were noticeably different. Among the isolates, Acinetobacter junii NA 3-2 showed a significant increase in the specific activity of superoxide dismutase, catalase, and ascorbate peroxidase after exposure to 20 ppm chlorine. In the guaiacol peroxidase (GPX) assay, only isolates belonging to Serratia marcescens showed GPX activity, and Serratia marcescens 3929-1 showed significant increase after exposure to 20 ppm of chlorine. None of the isolates belonging to Acinetobacter spp. showed GPX activity. Additionally, almost all control samples exhibited some enzyme activity, which may explain their survival against chlorine treatment in reservoirs. Principal component analysis revealed no strain-dependent similarities, while the balance of scavenging enzymes changed, as demonstrated in the heat map. Thus, this study suggests that antioxidant enzymes may be one mechanism of protection for some bacterial species against oxidative stress from chlorination, resulting in chlorine resistance. Understanding the mechanism of chlorine resistance is critical to identifying potential solutions. This study highlights the need to consider more modern approaches to disinfecting drinking water. Full article

(This article belongs to the Special Issue Sustainable Chemical Engineering: Adsorption and Water Disinfection)

► Show Figures

Figure 1

13 pages, 1425 KiB

Open AccessArticle

Reduction of Lead and Antimony Ions from the Crystal Glass Wastewaters Utilising Adsorption

by Alenka Ojstršek, Natalija Gorjanc and Darinka Fakin

Sustainability 2021, 13(20), 11156; https://0-doi-org.brum.beds.ac.uk/10.3390/su132011156 - 09 Oct 2021

Cited by 5 | Viewed by 1284

Abstract

The presented research examined five adsorbents, i.e., zeolite 4A, a mixture of three zeolites (4A, 13X, and ZSM-5), natural zeolite (tuff), activated carbon, and peat, and their potential capability for removal of exceeded ions of lead (Pb), antimony (Sb), sulphates (SO₄²⁻ [...] Read more.

The presented research examined five adsorbents, i.e., zeolite 4A, a mixture of three zeolites (4A, 13X, and ZSM-5), natural zeolite (tuff), activated carbon, and peat, and their potential capability for removal of exceeded ions of lead (Pb), antimony (Sb), sulphates (SO₄²⁻), and fluorides (F⁻) from real wastewater generated in the crystal glass industry, which was previously treated in-situ by flocculation, with the aim to attain the statutory values for discharge into watercourses or possible recycling. The screening experiment evidenced that the tuff was the most suitable adsorbent for the reduction of Pb (93.8%) and F⁻ (98.1%). It also lowered wastewater’s pH sufficiently from 9.6 to 7.8, although it was less appropriate for the reduction of Sb (66.7%) as compared to activated carbon (96.7%) or peat (99.9%). By adjusting the pH of the initial wastewater to pH 5, its adsorption capacity even enlarged. Results from the tuff-filled column experiment revealed reduction of Pb up to 97%, Sb up to 80%, and F⁻ up to 96%, depending on the velocity flow, and thus it could be used for post-treatment (and recycling) of wastewaters from the crystal glass industry. Moreover, the system showed an explicit buffering capacity, but negligible reduction of the SO₄²⁻. Full article

(This article belongs to the Special Issue Sustainable Chemical Engineering: Adsorption and Water Disinfection)

► Show Figures

Figure 1

13 pages, 3592 KiB

Open AccessFeature PaperArticle

Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

by Muhammad A. Sabri, Ziad Sara, Mohammad H. Al-Sayah, Taleb H. Ibrahim, Mustafa I. Khamis and Oussama M. El-Kadri

Sustainability 2021, 13(2), 923; https://0-doi-org.brum.beds.ac.uk/10.3390/su13020923 - 18 Jan 2021

Cited by 8 | Viewed by 2045

Abstract

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with [...] Read more.

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m² g⁻¹ for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI). Full article

(This article belongs to the Special Issue Sustainable Chemical Engineering: Adsorption and Water Disinfection)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Sustainable Chemical Engineering: Adsorption and Water Disinfection

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (3 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI