Highly efficient rice straw utilization for poly-(γ-glutamic acid) production by Bacillus subtilis NX-2

Area of Science:

• Biotechnology
• Microbial Production
• Biomass Utilization

Background:

• Lignocellulosic biomass is a sustainable feedstock for biotechnological applications.
• Poly-(γ-glutamic acid) (PGA) is a versatile biopolymer with numerous industrial uses.
• Efficient utilization of agricultural waste like rice straw is crucial for economic and environmental sustainability.

Purpose of the Study:

• To investigate poly-(γ-glutamic acid) (PGA) production by Bacillus subtilis NX-2 using rice straw as a feedstock.
• To develop and optimize a co-fermentation strategy for enhanced PGA accumulation.
• To evaluate the economic feasibility of using rice straw for industrial-scale PGA production.

Main Methods:

• Two-stage hydrolysis of rice straw to obtain fermentable sugars.
• Characterization of Bacillus subtilis NX-2's sugar consumption patterns (xylose and glucose).
• Design and implementation of a co-fermentation strategy with continuous feeding in a 7.5L fermentor.

Main Results:

• Achieved maximum cumulative PGA production of 73.0 ± 0.5 g L⁻¹.
• Attained maximum PGA productivity of 0.81 g L⁻¹ h⁻¹ using the continuous feeding method.
• Reduced carbon source costs by 84.2% compared to glucose and 42.5% compared to cane molasses.

Conclusions:

• Rice straw is a feasible and efficient lignocellulosic feedstock for poly-(γ-glutamic acid) production.
• The developed co-fermentation strategy significantly enhances PGA yield and productivity.
• This approach offers a cost-effective and sustainable alternative for industrial-scale PGA manufacturing.