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Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant
Andrea Chiara Sansotera1, Chiara Ceresa1, Cesar Francisco Trejo2
1Department of Pharmaceutical Sciences, Università del Piemonte Orientale "A. Avogadro", 28100 Novara, Italy.
Microorganisms
|June 26, 2026
Summary
This study demonstrates using rice husk to produce biosurfactants via *Bacillus subtilis*. Optimized conditions significantly boosted surfactin yield, offering a sustainable alternative to petrochemical surfactants.
Area of Science:
- Biotechnology
- Microbial Production
- Green Chemistry
Background:
- Synthetic surfactants derived from petrochemicals pose environmental risks due to poor biodegradability.
- Biosurfactants offer eco-friendly alternatives with desirable properties but face challenges in cost-effective large-scale production.
- Agro-industrial waste like rice husk presents an underutilized renewable resource for bioprocesses.
Purpose of the Study:
- To evaluate rice husk as a substrate for biosurfactant (lipopeptide) production by endophytic *Bacillus subtilis* AC7.
- To optimize medium composition for enhanced biosurfactant yield.
- To investigate the impact of pretreatment on substrate utilization and production.
Main Methods:
- Plackett-Burman design for medium optimization, identifying key factors like nitrogen sources and pH.
- Application of combined laccase-amylolytic pretreatment to rice husk.
- Shake-flask and bench-scale fermentation experiments.
- Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) for product identification.
Main Results:
- Medium optimization identified specific nitrogen sources (NaNO3, NH4NO3) and pH 6.5 as critical for enhancing biosurfactant production.
- Surfactin production increased from 4.2 mg/L to 266-276 mg/L under optimized conditions.
- Combined pretreatment significantly improved substrate utilization, leading to higher biomass and metabolic activity.
- Bench-scale fermentation achieved a maximum surfactin concentration of 237.5 mg/L, with C15 surfactin homologue being dominant.
Conclusions:
- Rice husk is a viable and sustainable substrate for producing high yields of surfactin by *Bacillus subtilis* AC7.
- Optimized fermentation conditions and pretreatment strategies significantly enhance biosurfactant production efficiency.
- This process offers a promising, cost-effective, and environmentally friendly alternative to synthetic surfactants.
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