Analyzing the influence of microstructured surfaces on the lactic acid production of Lactobacillus delbrueckii lactis in a flow‐through cell system

Abstract

Microorganisms growing in biofilms might be possible biocatalysts for future biotechnological production processes. Attached to a surface and embedded in an extracellular polymeric matrix, they create their preferred environment and form robust cultures for continuous systems. With the objective of implementing highly efficient processes, productive biofilms need to be understood comprehensively. In this study, the influence of microstructured metallic surfaces on biofilm productivity was researched. To conduct this study, titanium and stainless steel sheets were polished, micromilled, as well as coated with particles. Subsequently, the metal sheets were exposed to the lactic acid producing Lactobacillus delbrueckii subsp. lactis under laminar and homogeneous flow conditions in a custom-built flow cell. A proof-ofconcept showed that biofilm formation in the system only occurred on the designated substratum. Following a 24-h batch cultivation for primary biofilm development, the culture was continuously provided with glucose containing medium. As different experimental series have indicated, the process resulted to be stable for up to eleven days. Primary metabolite productivity averaged around 6-7 g/(L h). Interestingly, the productivity was shown to be affected neither by the type of metal, nor by the applied microstructures. Nevertheless, a higher dry biomass weight determined on micro-milled substratum indicates a complementary differentiation of biofilm components in future experiments.

Monitoring of biofilms grown on differentially structured metallic surfaces using confocal laser scanning microscopy

“…Previous studies on other microorganisms have proven an influence of the surface topography and/or the material used on attachment and growth, as well as production of compounds by biofilms [21,35,36]. Furthermore, Singh et al [37] suggested a relationship between surface roughness and bacterial attachment in that they are inversely related beyond a specific threshold.…”

“…Previous studies on other microorganisms have proven an influence of the surface topography and/or the material used on attachment and growth, as well as production of compounds by biofilms . Furthermore, Singh et al.…”

“…A custom‐designed flow cell previously described in Schlegel et al. was used for cultivation (Figure ). The flow cell consisted of a stainless steel frame (1.4571, EN X6CrNiMoTi17‐12‐2) with polyether ether ketone embedded stainless steel nozzles ( d = 1.5 mm; 1.4571, EN X6CrNiMoTi17‐12‐2), the substratum of choice (available surface for growth: 200 mm 2 ) and a glued‐on cover slip (Hecht‐Assistent 20 × 60 mm controlled thickness 0.17 mm ± 0.01 mm, Glaswarenfabrik Karl Hecht GmbH & Co KG, Sondheim/Rhoen, Germany).…”

Quantitative proteomic analysis of Lactobacillus delbrueckii ssp. lactis biofilms

“…All flow cell design parameters and operational settings were identical to those described previously . Briefly, flow cells were constructed with a flow channel volume of 8.75 mL and either a smooth (S) or microetched (ME) bottom surface as a substrate for the attachment of cells and development of a biofilm.…”

“…Briefly, flow cells were constructed with a flow channel volume of 8.75 mL and either a smooth (S) or microetched (ME) bottom surface as a substrate for the attachment of cells and development of a biofilm. Micro‐etching of the flow cell surface was conducted in response to previous results indicating that ME surfaces promoted the development of L. delbrueckii lactis biofilm . During biofilm cultivation, each flow cell (ME and S) was run in a continuous loop to a separate reservoir (MRS medium, pH 7.0, 45°C) for 24 h at a flow rate of 5 mL/min in intervals of 15 min on and 60 min off.…”