Efficient Preparation of Sophorolipids and Functionalization with Amino Acids to Furnish Potent Preservatives

Abstract

The development of new preservatives is an ongoing investigation in the food industry, especially those which are safe and environmentally friendly. In this study, biosurfactant sophorolipids (SLs) functionalized with amino acids were developed as efficient preservative agents. SLs were first isolated from fermentation broth by Candida bombicola ATCC 22214, hydrolyzed, and purified by extraction. The typical recovery is around 70%, while the extracted material consists of over 90% deacetylated acidic SLs (SL-COOH). Four types of SL derivatives were then synthesized via dicyclohexylcarbodiimide amidation reactions from prepared SL-COOH. Among the derivatives produced, the arginine SL conjugates (SL-D-Arg) displayed the highest activity against Grampositive bacteria and fungi and even inhibited the cell growth of Gram-negative bacteria and mildew. Furthermore, the arginine conjugates performed the broadest antimicrobial activity among the derivatives evaluated. The sterilization dosage of the arginine conjugates against the food-spoilage pathogen Bacillus spp. was 63−125 mg/L, in contrast to 250 mg/L for the enterotoxin producer Staphylococcus aureus and 500 mg/L for fungi. More importantly, SL-D-Arg displayed excellent biocompatibility, with a therapeutic index of over 7.94. SL-D-Arg has excellent potential as an alternative to traditional chemical preservatives.

Sophorolipid Candidates Demonstrate Cytotoxic Efficacy Against 2D And 3D Breast Cancer Models

“…Furthermore, the HC 50 values determined for both DLSL and SL-EE-D are each approximately 125 μg/mL ( Figure 9) . These HC 50 values are similar to those previously reported for other SL-analogues 53,54 ; however, this is the first report of erythrocyte toxicity for DLSL and SL-EE-D. Considering that the MDA-MB-231 IC 50 values are lower for DLSL than for SL-EE-D at all tested morphologies (2D, 2.5D, 3D), the similarity in HC50 values suggests DLSL possesses greater cancer cell specificity than SL-EE-D. We were unable to generate an HC50 value for doxorubicin due to the autofluorescence of the compound interefering with the fluorescence of erythrocyte lysis.…”

“…Furthermore, the HC 50 values determined for both DLSL and SL-EE-D are each approximately 125 μg/mL (Figure 9). These HC 50 values are similar to those previously reported for other SL-analogues 53,54 ; however, this is the first report of…”

Preparing Biosurfactant Glucolipids from Crude Sophorolipids via Chemical Modifications and Their Potential Application in the Food Industry

“…Under negative ion mode, the most notable products of GLs at m/z = 459.295 and ASLs at m/z = 621.348 could be caused by [M-H] − (Figure 3C), which has been confirmed in the positive ion mode. 16,23 The m/z difference between ASLs and GLs was 162.053, corresponding to the change brought about by the removal of a glucose group, which is in line with expectations. In the positive ion mode of GLs-Me (Figure S2), the signals at m/z 492.355, 497.306, and 513.280 were probably outcomes of [M + NH 4 ] + , [M + Na] + , and [M + K] + , respectively, confirming the presence of GLs-ME in the intermediate products after stage 1 of the reaction.…”

“…Free sugar (C 2 ) in the sample was subtracted from the measurement and quantitatively determined using HPLC (LC-20AD, refractive index detector RID-10A, Shimadzu, Japan) equipped with a Bio-Rad Aminex HPX-87H column. 16 The glucose concentration contribution from GLs was determined as the difference between C 1 and C 2 . The recovery at each step was calculated using the following equation:…”

“…Acidic sophorolipids (ASLs) were subsequently obtained from crude SLs via chemical modifications and stepwise extractions, as described before. 16 The crude SLs were mixed with 2 M NaOH, stirred at 95 °C with reflux for 80 min, and cooled to room temperature in an ice bath. Next, the resulting alkaline solution was blended with 0.46 M H 2 SO 4 to obtain a pH below 1.0.…”