Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production

Sansotera, Andrea Chiara; Ceresa, Chiara; Trejo, Cesar Francisco; Ferrandi, Alex; Allegrone, Gianna; Aprile, Silvio; Rinaldi, Maurizio; Morel, Silvia; Fracchia, Letizia

doi:10.3390/microorganisms14061288

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Open AccessArticle

Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production

by

Andrea Chiara Sansotera

^1,†

,

Chiara Ceresa

^1,†

,

Cesar Francisco Trejo

²,

Alex Ferrandi

¹

,

Gianna Allegrone

¹,

Silvio Aprile

^1,3

,

Maurizio Rinaldi

¹

,

Silvia Morel

^1,*

and

Letizia Fracchia

^1,*

¹

Department of Pharmaceutical Sciences, Università del Piemonte Orientale “A. Avogadro”, 28100 Novara, Italy

²

ROELMI BIOTECH Srl, 21040 Origgio, Italy

³

Novanalitica Srls, 28100 Novara, Italy

^*

Authors to whom correspondence should be addressed.

^†

These authors contributed equally to this work.

Microorganisms 2026, 14(6), 1288; https://doi.org/10.3390/microorganisms14061288

Submission received: 31 March 2026 / Revised: 22 May 2026 / Accepted: 25 May 2026 / Published: 7 June 2026

(This article belongs to the Special Issue Advances in Microbial Surfactants: Production and Applications (2nd Edition))

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Abstract

Nowadays, approximately 50% of chemical surfactants come from petrochemical sources and pose environmental risks due to poor biodegradability, affecting microbial communities, aquatic organisms, and terrestrial ecosystems. Biosurfactants are eco-friendly alternatives, thanks to their strong surface tension-reducing activity, stability, low toxicity, and biodegradability, but their large-scale production is still limited by high costs and low yields. In this study, rice husk was evaluated as a renewable substrate from the agro-industrial field for lipopeptide production by the endophytic Bacillus subtilis AC7. Medium optimization through Plackett–Burman designs identified nitrogen sources and pH 6.5 as key factors enhancing biosurfactant production. Under optimized conditions, surfactin production increased from 4.2 mg/L in untreated rice husk to 266–276 mg/L with NaNO₃ and NH₄NO₃ supplementation, respectively. Combined laccase–amylolytic pretreatment further improved substrate utilization, enhancing sugar availability and supporting higher biomass and metabolic activity. In bench-scale fermentation, this condition yielded the highest surfactin concentration (237.5 mg/L). LC-MS/MS analysis confirmed surfactin as the main product, with C15 as the dominant homologue, in both shake-flask and bench-scale fermentations. These findings highlight a novel, sustainable process for surfactin production, offering a renewable alternative to synthetic surfactants while addressing both environmental and economic concerns.

Keywords: agro-wastes; Bacillus subtilis; biosurfactant; fermentation; lipopeptide; Plackett–Burman experimental design; rice husk; surfactin; sustainable production

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MDPI and ACS Style

Sansotera, A.C.; Ceresa, C.; Trejo, C.F.; Ferrandi, A.; Allegrone, G.; Aprile, S.; Rinaldi, M.; Morel, S.; Fracchia, L. Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production. Microorganisms 2026, 14, 1288. https://doi.org/10.3390/microorganisms14061288

AMA Style

Sansotera AC, Ceresa C, Trejo CF, Ferrandi A, Allegrone G, Aprile S, Rinaldi M, Morel S, Fracchia L. Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production. Microorganisms. 2026; 14(6):1288. https://doi.org/10.3390/microorganisms14061288

Chicago/Turabian Style

Sansotera, Andrea Chiara, Chiara Ceresa, Cesar Francisco Trejo, Alex Ferrandi, Gianna Allegrone, Silvio Aprile, Maurizio Rinaldi, Silvia Morel, and Letizia Fracchia. 2026. "Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production" Microorganisms 14, no. 6: 1288. https://doi.org/10.3390/microorganisms14061288

APA Style

Sansotera, A. C., Ceresa, C., Trejo, C. F., Ferrandi, A., Allegrone, G., Aprile, S., Rinaldi, M., Morel, S., & Fracchia, L. (2026). Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production. Microorganisms, 14(6), 1288. https://doi.org/10.3390/microorganisms14061288

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Bacillus subtilis AC7 Fermentation on Rice Husk Substrate: A Sustainable Approach for Lipopeptide Biosurfactant Production

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