Sustainable production of sophorolipid biosurfactants using renewable cellulose-derived feedstocks

Abstract

Glycolipids produced and secreted by oleaginous yeasts are renewable compounds with important physico-chemical properties, and multiple biological and industrial applications. The large-scale production of these compounds has been limited by high production costs and low yields. The sophorolipid-producing yeast Pseudohyphozyma bogoriensis may possess the ability to grow in fermentation systems using carbon substrates deriving from inexpensive lignocellulosic biomass, while simultaneously secreting high value biomaterials. In this study, comparative analyses between different cellulose-derived carbon sources including glucose, cellobiose, and sodium carboxymethyl cellulose confirmed the ability of P. bogoriensis to grow and accumulate glycolipids using these substrates. On a dry weight basis, the highest yields of about 4% (wt/wt) glycolipids were obtained when cellobiose was supplemented at 10 g/L in shake-flask fermentations. When the unconventional carbon substrate sodium carboxymethyl cellulose was supplemented, cultures exhibited a lower glycolipid yield of 0.3% (wt/wt), but the dry weight was higher compared to other substrates. Analytical analyses using various chromatography methods confirmed the chemical profiles, whereas both monoacetylated and diacetylated sophorolipid forms with 22 carbon long-chain hydroxy fatty acid were identified in all glycolipid extracts. Surface tension (ST) and critical micelle concentration (CMC) measurements showed that glycolipids produced on cellulose-derived substrates exhibited similar or even superior physical properties compared with glucose. Furthermore, availability of the yeast genome sequences facilitated the identification of putative genes that may be involved in cellulose hydrolysis (e.g., cellulase-like). Information on genomic and metabolic pathways is a prerequisite for trait improvement toward increasing the production of high value biomaterials.