Low‐Temperature Crystallization for Separating Monoacetylated Long‐Chain Sophorolipids: Characterization of Their Surface‐Active and Antimicrobial Properties

Abstract

Pseudohyphozyma (formerly Rhodotorula) bogoriensis synthesizes long-chain-length (22-carbon chain) sophorolipids (22:0-SL) that are variously acetylated at the 6 0 -or/and 6 00 -carbons of the sophorose unit. In this paper, we describe a low-temperature crystallization protocol that preferentially separates the 6 0 -monoacetylated 22:0-SL (6 0 -Ac 1 -22:0-SL) from a parental mixture of 22:0-SL containing a majority (64.7%) of the 6 0 ,6 00diacetylated moiety (6 0 ,6 00 -Ac 2 -22:0-SL), as deduced from high-pressure-liquid-chromatography evaporative-lightscattering-detection (HPLC-ELSD) and LC/Q-TOF-MS analyses. Tensiometry measurements using the Wilhelmy plate method yielded minimum-surface-tension (SFT min ) andcritical-micelle-concentration (CMC) values of 34.6 AE 1.0 mN m −1 and 0.014 mM, respectively, for 6 0 -Ac 1 -22:0-SL (CRYSTAL) fraction and 34.9 AE 1.0 mM m −1 (SFT min ) and 0.018 (CMC) for the hexane precipitate (Hx-PRCP) fraction containing a high concentration (89.2%) of the diacetylated 6 0 ,6 00 -Ac 2 -22:0-SL after crystal removal. In contrast, the SFT min and CMC of the well-studied 16-18 carbon (C 16-18) -SL of Starmerella bombicola were 35-37.2 mN m −1 and 0.05-(>0.3) mM, respectively. Individually, the purified CRYSTAL and Hx-PRCP fractions exhibited a similar degree of strong growth-inhibition activity against Cutibacterium (formerly Propionibacterium) acnes as determined by an agar-plate zone of inhibition assay. Study on the growth inhibition of oral health-related bacteria, i.e., Streptococcus mutans and Lactobacillus acidophilus, showed that, depending on the bacteria and strains tested, the CRYSTAL fraction was either slightly better than or equally effective as the Hx-PRCP fraction in inhibiting cell growth. Fig. 1 Structures of sophorolipids. (a) 13-hydroxydocosanoic acid-sophorolipid (22:0-SL). (b) Lactonic 17-hydroxy-Δ9-octadecenoic acidsophorolipid (18:1-SL). R = -H or -Acetyl. The carbons at 6 0 -and 6 00 -position are indicated by arrows 554 J Surfact Deterg J Surfact Deterg (2020) 23: 553-563 555 J Surfact Deterg J Surfact Deterg (2020) 23: 553-563

Draft Genome Sequence of the Sophorolipid-Producing Yeast Pseudohyphozyma bogoriensis ATCC 18809

“…P. bogoriensis produces a structurally unique sophorolipid composed of 13-hydroxydocosanoic acid ( 4 – 8 ), with increasing industrial applications ( 5 , 9 ). These molecules have antimicrobial properties and have been suggested as anti-inflammation and anticancer compounds ( 10 – 14 ). Achieving substantial improvements through genetic manipulations necessitates an understanding of the gene content.…”

Sophorolipids—Bio-Based Antimicrobial Formulating Agents for Applications in Food and Health

“…The authors in that study observed antimicrobial efficiency on Propionibacterium acnes by sophorolipids embedded in different composite films such as plant-based composites pectin and alginate [ 90 ] and poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHB/HV) composites [ 91 ]. Solaiman et al [ 92 ] demonstrated that long carbon chains of acidic sophorolipids (22 carbon chains) had the strongest antibacterial effects on the tested bacteria Cutibacterium acne compared to the others including the lactonic form of sophorolipids consisting of 18 carbon chains only [ 92 ]. These results suggest that 22:0 sophorolipids are better suited biosurfactants as they possess antimicrobial properties for various applications [ 92 ].…”

“…Solaiman et al [ 92 ] demonstrated that long carbon chains of acidic sophorolipids (22 carbon chains) had the strongest antibacterial effects on the tested bacteria Cutibacterium acne compared to the others including the lactonic form of sophorolipids consisting of 18 carbon chains only [ 92 ]. These results suggest that 22:0 sophorolipids are better suited biosurfactants as they possess antimicrobial properties for various applications [ 92 ].…”

“…Waste glycerol as fermentation feedstock [82] A few studies highlighted the use of sophorolipids as natural antimicrobial agents for applications in skincare pharmaceutical formulations due to their non-toxic nature and good skin compatibility [90][91][92]. The authors in that study observed antimicrobial efficiency on Propionibacterium acnes by sophorolipids embedded in different composite films such as plant-based composites pectin and alginate [90] and poly(3-hydroxybutyric acid-co-3hydroxyvaleric acid) (PHB/HV) composites [91].…”

Preparation Process of Sophorolipids by Vacuum Freeze-Drying and Evaluation of Their Antimicrobial Activity

“…Currently, the preparation methods of SLs mainly include froth flotation, chromatography technology, crystallization at low temperature, membrane filtration, and extraction [13][14][15][16]. Among these methods, extraction technology is the most commonly used and the extractant is mainly ethyl acetate or ethanol (SLs-EAC, SLs-EtOH).…”