Enzymatic synthesis of N-alkanoyl-N-methylglucamide surfactants: solvent-free production and environmental assessment

Abstract

A biocatalysis based method for the solvent-free production of N-alkanoyl-N-methylglucamide (MEGA) surfactants was developed and used as a case study for the evaluation of different environmental assessment tools, such as the freeware package EATOS (Environmental Assessment Tool for Organic Synthesis). In order to also consider energy usage and process facilities, e.g. heating, stirring and vacuum, a complementary tool was needed; hence the EcoScale method and the use of an energy monitoring socket were also exploited. The solvent-free method followed by a simple hydrolysis step gave a final amide yield of 99% and a product essentially free of remaining substrate, N-methylglucamine (MEG). The latter is important since MEG can potentially be converted to carcinogenic nitrosamines. The absence of solvent in the reaction medium was also found to result in a significantly reduced potential environmental impact. The environmental tools used in this study were further scrutinized, and even if they represent some of the best freely available tools for evaluation of early stage process development, some points for further improvements are suggested.

Application of environmental and economic metrics to guide the development of biocatalytic processes

“…Furthermore, despite the negative and (often) the most critical impacts of some of the organic solvents [15,18], operating in an aqueous media does not represent a greener or cheaper solution [19] and thus, it is crucial to set guidelines for the substrate(s) and product(s) concentrations at which the biocatalyst should be able to operate effectively. To achieve these research targets, the biocatalyst must be improved either by process technologies (e.g., enzyme immobilization) or by rDNA technology.…”

“…In order to facilitate environmental assessments, several companies have developed in-house modified LCA methodologies and software tools, such as FLASC [42], BASF Eco-efficiency method [78], GREENSCOPE [79] [a Waste Reduction Algorithm (WAR [80]) based software], EATOS [81] and EcoScale [82]. Nevertheless, the simpler approaches still require a defined process (i.e., defined solvent, auxiliaries, upstream and DSP) and are thus not suitable for the previous development stage (Phase II: early development) when neither the biocatalyst and process are under development; whereas, to be used at Phase III, many of the above-mentioned tools fail on providing an objective (e.g., EcoScale penalties does not distinguish the amount of solvent or reaction time [15]) and a complete picture of the environmental impacts (e.g., EATOS and BASF methods are exclusively based on the mass metrics and on potential toxicity impacts and safety of the materials used, while the other impact categories are not accounted for [15]). Hence, at a later development stage, only an evaluation based on the LCA methodology will be able to give a fair judgment of the environmental performance.…”

“…Indeed, many of the potentially most interesting biocatalytic reactions, and their corresponding biocatalysts, are still under development and, as a result, many of the reactions are neither well developed nor optimized. There are a number of previously published studies reporting the benefits of biocatalytic processes in terms of their score on the environmental assessment [13][14][15], economic evaluation [16,17] and both economic and environmental assessments [18,19]. However, these studies refer to optimized processes and/or biocatalysts and thus, the use of more complete and complex tools for early development of the next generation of biocatalytic processes is not relevant.…”

Environmentally evaluated HPLC-ELSD method to monitor enzymatic synthesis of a non-ionic surfactant

“…Fatty acid glucamides can also be synthesised enzymatically using lipases as catalysts [3,4]. The enzymatic synthesis of AGs using MEG and fatty acid or fatty acid methyl ester yields a mixture of amide (surfactant) and amide-ester as a by-product (see Scheme 1) [5].…”

A Comparative Environmental Assessment for the Synthesis of 1,3-Oxazin-2-one by Metrics: Greenness Evaluation and Blind Spots

“…3 However, carrying out a LCA study on a chemical process is seldom possible due to the lack of all the necessary information needed especially in the case of new synthetic pathways. 4 Furthermore, the FLASC tool is not freely available for public users, 5 and Ecosolvent focuses mainly on the quantification of the environmental impact of waste solvent treatment. As a consequence, recently, a set of measures, i.e., green metrics, have been developed in order to enable the assessment of chemical processes and to monitor their environmental impacts.…”