Location: Biobased and Other Animal Co-Products
Project Number: 8072-41000-090-00
Start Date: Jul 22, 2010
End Date: Jul 21, 2015
Microorganisms capable of producing new variants of rhamnolipids (RLs) and sophorolipids (SLs) will be created by introducing mutated genes that originally encode the synthesis of native RL and SL. Increasing the RL yields in non-pathogenic P. chlororaphis by metabolic engineering will be attempted by increasing the copy-number and transcription level of the responsible genes (i.e., rhlAB), or by ‘knocking out’ the gene(s) responsible for diverting precursors away from RL biosynthesis. We will also enhance the value of P. chlororaphis by introducing another gene, rhlC, to allow the biosynthesis of dirhamnose lipids. The efficiency of RL- and SL-producing microorganisms to utilize soy molasses (SM) will be improved by introducing genes encoding enzymes that breakdown the complex sugars in SM. We will also express in Candida bombicola (an SL-producing yeast) and P. chlororaphis the genes that are used for glycerol metabolism to improve the organisms’ efficiency of using bioglycerol. To enhance colonization and biofilm formation for higher RL yields from P. chlororaphis, we will experiment with attaching a sponge-like adapter to the impellers of a fermenter and then use minimal aeration (slow impeller rotation, reduced air introduction, or both). Separately, process optimization will be carried out for the fermentative synthesis of SL, gamma-polyglutamic acid (PGA) and cyanophycin (Cp) using such low-cost feedstocks as crude glycerine from biodiesel production, soy molasses and meat and bone meal hydrolysates. Fermentation parameters such as carbon source content and concentration, feed rate, aeration, pH etc. will be varied and optimized using Response Surface Methodology (RSM). To increase the values of bio-product subcomponents or for application in end-use products, biological and chemical syntheses will be performed to obtain the followings for subsequent characterization: 1) novel epoxy and polyhydroxy fatty acids by using functionalized fatty acids (i.e., vernolic acid, ricinoleic acid, lesquerellic acid) as fermentative substrates, 2) cyanophycin-derived biosurfactants by linking fatty acids to the polar dipeptide unit of Cp, 3) terminally unsaturated fatty acids by elimination reactions on hydroxy fatty acids, 4) biopolymer/biosurfactants composites by solution-casting of PHA and SL or RL, 5) oligoamides by converting the hydroxy fatty acids to amino fatty acids and self-coupling them, and 6) water-soluble SLs by linking charged amino acids to the sugar headgroups.