Author ORCID Identifier

https://orcid.org/0009-0008-5461-512X

Biosketch

I am Srividhya Krishnan, a Ph.D. graduate in Biotechnology with an academic background in Biotechnology engineering at both undergraduate and postgraduate levels. My research has focused on the valorization of waste into commercially valuable products, integrating multidisciplinary approaches. I have strong expertise in thermochemical conversion processes, particularly pyrolysis, and have also worked extensively on the microbial and molecular biology aspects of product testing.

Date of Award

17-8-2025

Document Type

Thesis

School

School of Chemical & Biotechnology

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Prof. V. Ponnusami

Second Advisor

Dr. P. Nithyanand

Keywords

Pyrolysis, Biofilms, Disinfectant, Aqueous phase, Pathogens

Abstract

Hospital-acquired infections (HAIs) significantly contribute to the emergence and spread of antimicrobial resistance (AMR), primarily through the contamination of high-touch surfaces. Current disinfectants have drawbacks like high environmental persistence, ecotoxicity, and resistance development, prompting the need for environmentally friendly alternatives.

One potential approach is pyrolysis, during which the biomass components are broken down into solid, liquid, and pyro-gas. The aqueous phase of the liquid fraction is usually discarded as waste, but it contains a variety of organic compounds that have the potential for antibacterial and antifungal activity. The present study assessed the anti-infective and anti-biofilm properties of wheat straw pyrolysis aqueous phase (WS AQ) under nine conditions.

The WS AQ showed antimicrobial activity against drug-resistant nosocomial pathogens like Acinetobacter baumannii, Methicillin-resistant Staphylococcus aureus (MRSA), and Candida auris, and showed 62%-74% matured biofilm disruption ability under mono and polymicrobial conditions. It also downregulated virulence genes involved in quorum sensing and biofilm formation. The study evaluated the storage stability of WS AQ over 60 days at different storage conditions (25 °C, 4°C, and -20°C), revealing no significant changes in functional groups or antimicrobial activity, indicating its long-term stability.

Further, we xxiii evaluated three major compounds, furfuryl alcohol, 2-methyl-2-cyclopentenone, and guaiacol, as inhibitors from the aqueous phase. The compounds showed an additive effect and biofilm eradication of 52% on preformed biofilms. They also showed a reduction in quorum sensing and biofilm adhesion gene expressions. A disinfectant formulation containing EDTA, ethanol, SLS, and AQ was developed and tested for efficacy.

The phenol coefficient of two (for mixed species) was observed, implying that the disinfectant formulation is more potent and efficient. A custom-made Centre for Disease Control and Prevention (CDC) biofilm reactor was fabricated to mimic clinical biofilms. The biofilms were allowed to form on stainless steel 316 coupons, and the formulated disinfectant efficacy was evaluated. The toxicity of the formulation was further assessed using the filter paper contact test using earthworms as a biological model.

Based on our study findings, WS AQ showed antimicrobial and antibiofilm properties, highlighting its stability and efficacy against drug-resistant nosocomial pathogens, suggesting a promising, environmentally sustainable alternative for infection control and biofilm management in healthcare settings.

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