Foam fractionation for promoting rhamnolipids production by Pseudomonas aeruginosa D1 using animal fat hydrolysate as carbon source and its application in intensifying phytoremediation

Animal fat is a residue generated from meat processing industries. In the current work, animal fat has been used as carbon source for producing rhamnolipids by Pseudomonas aeruginosa D1. The synthesized rhamnolipids were used to intensify phytoremediation of heavy metal-contaminated soils. First, animal fat was degraded by alkaline and enzymatic hydrolysis methods. Experimental results indicated that the animal fat hydrolysate of alkaline hydrolysis could increase the rhamnolipids yield with a high proportion of mono-rhamnolipids. For achieving the continuous production and separation of rhamnolipids, a coupling strategy of foam fractionation and fermentation with feeding carbon source was developed. Under the conditions of feed flow rate of animal fat hydrolysate 2.0 mL/min, gas volumetric flow rate 90 mL/min and inoculation scale 6.0 %, the yield and recovery percentage of rhamnolipids were 25.8 g/L and 93.4 %, respectively. The synthesized rhamnolipids could significantly improve the activity of soil enzymes for facilitating the digestion and transformation of heavy metals from soils toward the above-ground part of ryegrass.