Conversion of Methane into Polyhydroxybutyrate using Methylosinus trichosporium NCIMB 11131: Applications in Food Packaging, Bone Tissue Engineering, and Electronics
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2023
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Abstract
The Industrial Revolution led to significant increases in atmospheric greenhouse gases, with methane, the second most harmful, rising from 700 ppb to 1922 ppb by 2022. Methane has a 25-fold greater infrared absorption potential than CO2, contributing significantly to global warming. At current emission rates, the planet is on track for a 2°C temperature rise by 2036, highlighting the urgency for innovative solutions. Simultaneously, plastic pollution has emerged as a critical issue, with over 450 million tons produced annually, of which only a small fraction is recycled. As both methane emissions and plastic waste continue to rise, sustainable alternatives are required. This study addresses these challenges by utilizing Methylosinus trichosporium NCIMB 11131, a Type-II methanotrophs, to convert methane into polyhydroxybutyrate (PHB), an eco-friendly, biodegradable bioplastic. PHB production is induced under nitrogen-starved conditions, using methane as a carbon source. This dual-purpose approach mitigates methane emissions while producing a sustainable alternative to traditional plastics. Optimal conditions yielded PHB content of 57.3% (w/w), with a production rate of 1.11 g.L-1.d-1 in a 5-L bioreactor, demonstrating scalability. Further process optimization included maximizing methane mass transfer using sparger and silicone oil vectors in airlift reactor. Applications of PHB were explored in three sectors: food packaging, bone tissue engineering, and electronics. PHB films exhibited excellent mechanical properties, degradability, and moisture resistance, making them suitable for sustainable packaging. In bone tissue engineering, a composite of PHB and hydroxyapatite derived from waste eggshells demonstrated biocompatibility and osteo-conductivity, promoting cell attachment and proliferation. In electronics, PHB films served as insulating covers for batteries, displaying significant electrical insulation and heat resistance. This research highlights the potential of M. trichosporium NCIMB 11131 for PHB production using methane as a carbon source, with diverse industrial applications. The study advances sustainable bioplastic production, contributing to both greenhouse gas reduction and a circular economy.
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Supervisor: Das, Debasish