LactiFilm – Hydrogel supported co-culture biofilms of lactobacilli and phytoplankton for sustainable production of lactic acid

• Applicants: Professorin Dr. Regine von Klitzing; Dr. Shrikrishnan Sankaran; Professorin Dr. Marie Weinhart
• Subject Area: Biological Process Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559396548

LactiFilm will explore the possibility of establishing compartmentalized co-culture biofilms between photoautotrophs and productive bacteria, powered primarily by light and CO2, to sustainably produce an industrial compound. The co-culture will include phytoplankton and lactobacilli, whose growth, metabolism, and spatial distribution will be individually controlled by compartmentalized encapsulation within mechanically and structurally tunable hydrogel films. These co-culture biofilms will be developed to produce lactic acid, a critical bulk chemical used in several industries and facing increasing demand for the production of polylactic acid (PLA) based biodegradable plastics. The global demand for lactic acid is expected to surpass 19 million tons by 2025, yet current microbial production methods face several challenges like high feedstock costs, energy consumption in fermentation processes, and the complex purification required for PLA synthesis. LactiFilm addresses these issues through multi-layered hydrogel-supported biofilms with properties tailored to (i) maintain a self-replenishing phytoplankton feedstock that can be partially lysed on demand with a remote trigger, (ii) constrain lactobacillus growth in favor of lactic acid production, and (iii) release lactic acid in a flow cell with minimal impurities for polymerization into PLA. This will be achieved by combining expertise in biotechnology and materials science. The biotechnological developments will involve first identifying optimal phytoplankton strains to support lactobacillus growth and production of optically pure lactic acid, then evolving the lactobacillus to efficiently metabolize phytoplankton lysates. The materials science developments involve creating polymeric and microgel components that can be assembled into hydrogel films encapsulating the bacteria. Furthermore, smart features like temperature-responsive stiffness changes or light-responsive local heating will be engineered into the gels for on-demand partial lysis of the phytoplankton. These multi-layered co-culture biofilms will be integrated in a flow reactor for continuous LA production that can be polymerized into PLA with minimal purification. This approach is expected to improve LA productivity and yield while minimizing feedstock costs and energy use. Thus, LactiFilm's results will support the development of scalable, sustainable biofilm-based production systems for use in white biotechnology.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2494: Productive Biofilm Systems