Efficient production and separation of biodegradable surfactants from cellulose in 1-butyl-3-methylimidazolium chloride

Transformation of Pectins into Non-Ionic or Anionic Surfactants Using a One-Pot and Cascade Mode Process

The present article describes the one-pot synthesis of double- and single-tailed surfactants by a cascade process that involves the hydrolysis/butanolysis of pectins into butyl galacturonate monosaccharides followed by transesterification/transacetalisation processes with fatty alcohols, and subsequent aqueous basic and acid treatments. The cascade mode allows the depolymerisation to proceed more efficiently, and the purification conditions are optimised to make the production of single-tailed surfactants more manufacturable. These products in a pure form or as mixtures with alkyl glycosides resulting from butanolysis and transglycosylation of pectin-derived hexoses, exhibit attractive surface-tension properties, especially for the n-oleyl ᴅ-galactosiduronic acid products. In addition, a readily biodegradability and an absence of aquatic ecotoxicity are shown for the galacturonic acid derivatives possessing an oleyl alkyl chain at the anomeric position.

Synthesis of long-chain alkyl glucosides via reverse hydrolysis reactions catalyzed by an engineered β-glucosidase

Long-chain alkyl glucosides, such as octyl and decyl β-d-glucopyranosides (OG and DG, respectively), are regarded as a new generation of biodegradable, non-ionic surfactants. Previously, the mutants of Dalbergia cochinchinensis Pierre dalcochinase showed potential in the synthesis of oligosaccharides and alkyl glucosides. In this study, the N189F dalcochinase mutant gave the highest yields of OG and DG synthesis under reverse hydrolysis conditions. The optimized yield of OG (57.5 mol%) was obtained in the reactions containing 0.25 M glucose and 0.3 units of the N189 F mutant in buffer-saturated octanol at 30 °C. The identity of OG and DG products was confirmed by high resolution mass spectrometry (HRMS) and NMR. Consistent with its capability for synthesis, the reactivation kinetics and ITC analysis revealed that the aglycone binding pocket of the N189F mutant was more favorable for long-chain alkyl alcohols than the wild-type dalcochinase, while their glycone binding pockets showed similar affinity for the glucosyl moiety. STD NMR revealed higher interactions at the aglycone sites than the glycone sites. Our results demonstrated a promising potential of the N189F dalcochinase mutant in the future commercial production of long-chain alkyl glucosides via reverse hydrolysis reactions.

Direct conversion of cellulose into ethanol and ethyl-β-d-glucoside via engineered Saccharomyces cerevisiae

Simultaneous saccharification and fermentation (SSF) of cellulose via engineered Saccharomyces cerevisiae is a sustainable solution to valorize cellulose into fuels and chemicals. In this study, we demonstrate the feasibility of direct conversion of cellulose into ethanol and a biodegradable surfactant, ethyl-β-d-glucoside, via an engineered yeast strain (i.e., strain EJ2) expressing heterologous cellodextrin transporter (CDT-1) and intracellular β-glucosidase (GH1-1) originating from Neurospora crassa. We identified the formation of ethyl-β-d-glucoside in SSF of cellulose by the EJ2 strain owing to transglycosylation activity of GH1-1. The EJ2 strain coproduced 0.34 ± 0.03 g ethanol/g cellulose and 0.06 ± 0.00 g ethyl-β-d-glucoside/g cellulose at a rate of 0.30 ± 0.02 g·L^-1 ·h^-1 and 0.09 ± 01 g·L^-1 ·h^-1 , respectively, during the SSF of Avicel PH-101 cellulose, supplemented only with Celluclast 1.5 L. Herein, we report a possible coproduction of a value-added chemical (alkyl-glucosides) during SSF of cellulose exploiting the transglycosylation activity of GH1-1 in engineered S. cerevisiae. This coproduction could have a substantial effect on the overall technoeconomic feasibility of theSSF of cellulose.

Disassembly of Bacterial Biofilms by the Self-Assembled Glycolipids Derived from Renewable Resources

More than 80% of chronic infections of bacteria are caused by biofilms. It is also a long-term survival strategy of the pathogens in a nonhost environment. Several amphiphilic molecules have been used in the past to potentially disrupt biofilms; however, the involvement of multistep synthesis, complicated purification and poor yield still remains a major problem. Herein, we report a facile synthesis of glycolipid based surfactant from renewable feedstocks in good yield. The nature of carbohydrate unit present in glycolipid influence the ring chain tautomerism, which resulted in the existence of either cyclic structure or both cyclic and acyclic structures. Interestingly, these glycolipids self-assemble into gel in highly hydrophobic solvents and vegetable oils, and displayed foam formation in water. The potential application of these self-assembled glycolipids to disrupt preformed biofilm was examined against various pathogens. It was observed that glycolipid 6a disrupts Staphylococcus aureus and Listeria monocytogenes biofilm, while the compound 6c was effective in disassembling uropathogenic E. coli and Salmonella enterica Typhimurium biofilms. Altogether, the supramolecular self-assembled materials, either as gel or as surfactant solution could be potentially used for surface cleansing in hospital environments or the food processing industries to effectively reduce pathogenic biofilms.

Transformation of Cellulose into Nonionic Surfactants Using a One-Pot Catalytic Process

Alkyl glucosides surfactants are synthesized by a cascade process that involves the methanolysis of cellulose into methyl glucosides followed by the transacetalization with n-octanol. The first step was performed using methanol as solvent and acid catalysts (such as, inorganic acids, heteropolyacids, ionexchange resins, or modified carbon materials). Subsequently, long-chain alkyl glucosides are obtained in the second step by transacetalization, which involves the reaction of methyl glucosides with a fatty alcohol using the same acid catalyst. The overall process was performed under mild conditions. Amorphous sulfonated carbon catalyst achieved the best results for the complete conversion of cellulose in methanol at 200 °C with methyl α,β-glucopyranosides yields higher than 80 %. Moreover, this material containing -SO₃ H groups is ideal to perform the second step to obtain octyl and decyl glucosides in yields higher than 73 % at 120 °C. In addition, the sulfonated carbon catalyst (C-SO₃ H) can be reused with only a slightly decrease of its activity after four consecutive cycles.