A novel solid-state, multi-layered biodegradable microbial inoculant system for rice straw composting: biocapsule...

Area of Science:

• Environmental Microbiology
• Biotechnology
• Waste Management

Background:

• Conventional liquid microbial inoculants for lignocellulosic waste composting face limitations due to environmental stress and uncontrolled release.
• Developing stable and effective microbial delivery systems is crucial for optimizing composting processes.

Purpose of the Study:

• To design and evaluate a multi-layered biodegradable biocapsule for sustained lignocellulolytic microbial activity in composting.
• To assess the composting efficiency of the biocapsule compared to conventional methods and controls.

Main Methods:

• A three-layered biocapsule was constructed using rice straw biocomposite, humic acid, activated carbon, corn starch, carboxymethyl cellulose, and calcium alginate beads with encapsulated *Klebsiella-Enterobacter* consortium immobilized on hydroxyapatite nanoparticles.
• The biocapsule's structure included an outer rice straw shell, a middle hydrogel layer for moisture retention, and a core of bacteria in calcium alginate beads.
• Composting efficacy was tested using intact biocapsules, powdered biocapsules, and a control group, with evaluations based on Sri Lankan Standards.

Main Results:

• Calcium alginate beads demonstrated high bacterial encapsulation (78.29%) and release (84.45%) efficiency, with significant bacterial colonization.
• The intact biocapsule achieved 56.16% biodegradation in 7 days and sustained thermogenesis above 55 °C for 25 days.
• Intact biocapsules significantly improved compost quality, increasing total nitrogen (71.89%), phosphorus (83.0%), and potassium (60.66%), reducing C:N ratio by 72.83%.

Conclusions:

• The developed multi-layered biocapsule effectively protects lignocellulolytic microbial inoculants, enhancing composting efficiency and compost quality.
• This biocapsule technology offers a promising solution for controlled microbial delivery in waste management, overcoming limitations of conventional liquid inoculants.