Enhanced iturin a production in a two-compartment biofilm reactor by Bacillus velezensis ND

Simultaneous Production of MK-7 and Iturin A by Bacillus velezensis ND

Bacillus velezensis can produce various secondary metabolites, such as the antibacterial compound iturin A and the coagulation-promoting menaquinone-7 (MK-7). To enhance the economic feasibility of the fermentation process, a co-production strategy, involving the simultaneous production of MK-7 and iturin A by Bacillus velezensis ND, was investigated in this study. Firstly, the effects of cultivation temperature and initial pH on the synthesis of MK-7 and iturin A were investigated. Considering the co-production of iturin A and MK-7, the optimal temperature and pH were determined as 32 °C and 7, respectively. Subsequently, important nutrients for the co-production process were investigated. It was observed that glycerol, soybean meal, yeast extract, and L-glutamate had a significant effect on the co-produce process. An optimal medium composed of glycerol (72.19 mL L-1), L-glutamate (1.4 g L-1), yeast extract (16.88 g L-1), and soybean meal (130.95 g L-1) was obtained by response surface methodology (RSM). This co-produce process was further scaled up in a biofilm reactor, and the maximum concentration of MK-7 and iturin A reached 46.88 mg L-1 and 5.58 g L-1, respectively. Finally, we established an effective method for separately extracting the two metabolites from the fermentation broth. The superiority of this co-production fermentation strategy demonstrates its significant potential for industrial production.

Process optimized for production of iturin A in biofilm reactor by Bacillus velezensis ND

In this research, to provide an optimal growth medium for the production of iturin A, the concentrations of key amino acid precursors were optimized in shake flask cultures using the response surface method. The optimized medium were applied in a biofilm reactor for batch fermentation, resulting in enhanced production of iturin A. On this basis, a step-wise pH control strategy and a combined step-wise pH and temperature control strategy were introduced to further improve the production of iturin A. Finally, the fed-batch fermentation was performed based on combined step-wise pH and temperature control. The titer and productivity of iturin A reached 7.86 ± 0.23 g/L and 65.50 ± 1.92 mg/L/h, respectively, which were 37.65 and 65.20% higher than that before process optimization.

Multispecies Bacterial Biofilms and Their Evaluation Using Bioreactors

Pathogenic biofilm formation within food processing industries raises a serious public health and safety concern, and places burdens on the economy. Biofilm formation on equipment surfaces is a rather complex phenomenon, wherein multiple steps are involved in bacterial biofilm formation. In this review we discuss the stages of biofilm formation, the existing literature on the impact of surface properties and shear stress on biofilms, types of bioreactors, and antimicrobial coatings. The review underscores the significance of prioritizing biofilm prevention strategies as a first line of defense, followed by control measures. Utilizing specific biofilm eradication strategies as opposed to a uniform approach is crucial because biofilms exhibit different behavioral outcomes even amongst the same species when the environmental conditions change. This review is geared towards biofilm researchers and food safety experts, and seeks to derive insights into the scope of biofilm formation, prevention, and control. The use of suitable bioreactors is paramount to understanding the mechanisms of biofilm formation. The findings provide useful information to researchers involved in bioreactor selection for biofilm investigation, and food processors in surfaces with novel antimicrobial coatings, which provide minimal bacterial attachment.

Enhanced exopolysaccharide production of Cordyceps militaris via mycelial cell immobilization on plastic composite support in repeated-batch fermentation

Repeated-batch fermentation with fungal mycelia immobilized in plastic composite support (PCS) eliminates the lag phase during fermentation and improves metabolite productivity. The strategy is implemented herein, and a novel modified PCS is developed to enhance exopolysaccharide (EPS) production from the medicinal fungus Cordyceps militaris. A modified PCS (SYE + PCS) was made by compositing polypropylene (PP) with a nutrient mixture containing soybean hull, peptone, yeast extract, and minerals (SYE+). The use of SYE + PCS has consistent cell productivity throughout the multiple fermentation cycles, which resulted in a more higher cell productivity after second batch compared to unmodified PCS. The cell grown on SYE + PCS also generates a higher yield of EPS (3.36, 6.93, and 5.72 g/L in the first, second, and third fermentation cycles, respectively) up to three-fold higher than the cell immobilized on unmodified PCS. It is also worth noting that the EPS from mycelium grown on SYE + PCS contains up to 2.3-fold higher cordycepin than those on unmodified PCS. The presence of nutrients in SYE + PCS also affects the hydrophobicity and surface roughness of the PC, improving mycelial cell adhesion. This study also provides a preliminary antioxidant activity assessment of EPS from immobilized C. militaris grown with SYE + PCS.