Metal Ions Can Affect The Composition And Production Of Sophorolipids By Wickerhamiella Domercqiae Y_2A CGMCC3798

Sophorolipids (SLs), as important extracellular glycolipid biosurfactants, can beused widely in food, cosmetics, cleaning, pharmaceutical and environmental industries,etc. It is the common opinion that sophorolipids secreted by yeasts in fermentation brothare a mixture since sophorolipids were discovered.They are divided into two mainforms of lactonic sophorolipids (L-SLs) and acidic sophorolipids (A-SLs). L-SLs havedifferent biological and physicochemical properties compared with A-SLs, which can beapplied as drugs due to their better antimicrobial, anticancer activity. Whereas theA-SLs display advantages in foam production, emulsification ability and solubility, theycan be applied in oil recovery, biodegradation and contaminant removal, skin moisture,food processing and detergence. Thus, it is necessary to develop a process for selectiveproduction of different sophorolipids.Now, what factors determine the ratio of L-SLs to A-SLs is still unclear. Theinfluences of metal ions on the composition of sophorolipids have not been addressed. Itis necessary to study metal ions how to affect the composition of sophorolipids by W.domercqiae Y2ACGMCC3798, metal ions added into media including Mg2+, Fe2+, Cu2+,Mn2+, Ni2+, Co2+, Fe3+, Zn2+respectively were tested in this work. The data of this workindicate the potential of the selective production of different sophorolipids based on theselection of metal ions to culture media.The main research aspects and results are as below:(1) To study the ability of Wickerhamiella domercqiae Y2ACGMCC3798togrow and produce sophorolipid in the presence of metal ions, the fermentation mediawas supplemented with Mg2+, Fe2+, Cu2+, Mn2+, Ni2+, Co2+, Fe3+, Zn2+ions respectivelyadded as sulphate at the same concentration of50mg/L. pH was effected slightly,remained at about2.5-3.0. In general, lower dry cell weight (DCW) was obtained thanthe control (without metal ions,10.13±0.12g/L). However, the degree of metal ionseffects on DCW varied with the types of ions. Fe2+ions showed the most significantimpact, DCW was5.93±0.31g/L. The impact on the total SLs was also hugely differentamong the metal ions tested in this experiment. When adding Ni2+, Mn2+or Cu2+, thetotal SLs was all more than100g/L, especially for Cu2+, the total SLs reached149.90g/L. However, the total SLs was about41.35g/L when only Fe2+ions existed. For others ions including Mg2+, Zn2+, Fe3+, Co2+, the total SLs was about80g/L.Furthermore, the percentage of A-SLs in total SLs was changed from28.76%to84.64%when adding different metal ions.28.25percent with Mg2+condition and84.64percent with Fe2+condition were obtained. The quality ratios of A-SLs to L-SLs were0.39and5.51, with50mg/L Mg2+and50mg/L Fe2+, respectively. So, Mg2+ions wereoptimal for L-SLs production and Fe2+ions were suitable for A-SLs production in thisexperiment.(2) Sophorolipids composition analysis,which were medium with Mg2+andFe2+,which was further investigated by TLC, HPLC and LC-MS analyses. More than20peaks in each sophorolipids mixture. Retention time of each peak was the same, butrelative peak area was obviously different, especially at21.26min,34.30min and38.66min. The results demonstrated that Mg2+and Fe2+greatly altered the proportion ofeach sophorolipid molecule in total SLs. In order to elucidate the structures ofsophorolipids which were medium with Cu2+identification of sophorolipids wasperformed by TLC, FT-IR, HPLC、HPLC-MS.The fatty acid of sophorolipids contains16or18carbon ions. the peaks from1to5were identified as acidic SLs, and thefractions from6to9were L-SLs.11kinds of sophorolipids were founded in Peaks1to10, including5kinds of A-SLs and6kinds of L-SL.(3) The researches for different metal ions affect the regulatory mechanism ofWickerhamiella domercqiae Y2ACGMCC3798. Firstly, we studied two different metalions affected the composition and composition of sopholipids. Secondly, the results ofSDS–PAGE and enzymatic transformation of acidic sophorolipids showed differentialexpression of extracellular proteins of Wickerhamiella domercqiae Y2ACGMCC3798adding Mg2+, Fe2+or Cu2+conditions. Lastly, enzymatic transformation of A-SLsdemonstrated that A-SLs have been partially transformed to L-SLs. However, the crudeenzyme from the cultures with MgSO47H2O led to produce more L-SLs than that fromthe cultures with FeSO47H2O.The results of enzymatic transformation of A-SLsrevealed that Fe2+ions inhibit cells to produce less enzymes related to L-SLsproduction.