Conversion of inulin-rich raw plant biomass to 2,5-furandicarboxylic acid (FDCA): Progress and challenge towards biorenewable plastics

Abstract

The current commercial plastic manufactures have been produced using petroleum-based resource. However, due to concerns over the resource depletion and the environmental sustainability, bioresource-based manufacturing processes have been developed to cope against these concerns. Bioresource-derived 2,5-furandicarboxylic acid (FDCA) can be utilized as a building block material for plastic manufactures. To date, numerous technologies have been developed for the production of FDCA using various types of bio-based feedstocks such as hydroxymethylfurfural (HMF), 6-C sugars, and polysaccharides. The commercial companies produce FDCA using HMF-based production processes due to their high production efficiency, but the high price of HMF is a problem bottleneck. Our review affords important information on breakthrough approaches for the cost-efficient and sustainable production of FDCA using raw plant feedstocks rich in inulin. These approaches include bioprocessing technology based on the direct use of raw plant feedstocks and biomodification of the target plant sources. For the former, an ionic liquid-based processing system is proposed for efficient pretreatment of raw plant feedstocks. For the latter, the genes encoding the key enzymes; sucrose:sucrose 1-fructoyltransferase (1-SST), fructan:fructan 1-fryuctosyltransferase (1-FFT), fructan 1-exohydrolase (1-FEH), and microbe-derived endoinulinase, are introduced for biomodification conducive to facilitating bioprocess and improving inulin content. These approaches would contribute to cost-efficiently and sustainably producing bio-based FDCA.

Introduction

The subject of biorenewable polymers is at the center of a pivotal issue in the current plastic manufacturing industry because of their positive impact on global resource depletion and environmental sustainability. These polymers can be produced through the conversion process of biomaterial sources such as plant biomass and plant-derived materials including agricultural residues and other biowastes (Bhatia et al., 2021; Heo et al., 2019, Heo et al., 2020, Heo et al., 2021). The petroleum-based polymers that have been used as feeding materials for the production of commodity plastics (packaging, food containers, and household products, etc.) can be substituted by these polymers derived from the bio-based feedstocks. For example, petroleum-derived PET (polyethylene terephthalate), which has been used to manufacture plastic bottles, can be replaced by PEF (polyethylene 2,5-furandicarboxylate) that can be produced from the feedstocks originated from bioresources and other waste materials. Several venture companies (e.g., Avantium, Corbion, Synvina) are currently in progress towards the marketable production of PEF using FDCA (2,5-furandicarboxylate) (Hwang et al., 2020; Jiang et al., 2020).

FDCA is a monomeric platform intermediate with a cyclic structure belonging to furan chemical groups. It can be readily converted into various value-added chemical products such as; biochemicals (e.g., isoamyl furandicarboxylate, diphenyl furan-2,5-dicarboxylate, etc.), ingredients (Hexanoic acid, macrocyclic ligands, etc.), and commodity polymers (polyesters, polyamides, etc.) (Fig. 1). Due to its wide spectrum of industrial applications and future enormous market potential, FDCA has been classified as an economically feasible platform chemical by the US Department of Energy (DOE). Currently, several venture companies produce FDCA at a commercial scale and demo/pilot plant levels through the oxidation process of HMF (hydroxymethylfurfural) that can be prepared from bio-based feedstocks by way of the dehydration process of bio-based feedstocks (Heo et al., 2019, Heo et al., 2020, Heo et al., 2021; Yi et al., 2014a, Yi et al., 2015a). For example, Dutch renewable chemistry venture company, Avantium has planned to build a 5000 t/y production facility for FDCA using YXY processing technology, which is based on HMF (hydroxymethylfurfural) oxidation process (Table 1) (Avantium, 2020). Other companies also use HMF-based processing systems for the production of FDCA (Table 1). As such, it is evident that HMF is a pivotal player in the current production process of FDCA. Although numerous achievements on HMF-based FDCA production process have been accumulated, its production technologies are not yet fully market-driven, remain technology-driven due mainly to the limited supply of HMF caused by its high price (Cai et al., 2021; Chen et al., 2021; Hameed et al., 2020; Sajid et al., 2018). Accordingly, today's most critical challenge for the marketable production of FDCA should be pointed to the further reduction of its production cost. Our review affords the paramount platform strategies conducible to this challenge by introducing two strategic approaches. One approach is dependent on the use of raw biomass feedstock rich in inulin polymer, which can be used as a feeding substrate for the production of FDCA. Another is dependent on the utilization of biomodification technology conducive to its cost-effective production.

In industrial chemical manufacturing, the use of raw biomass feedstocks is more favorable from a low-carbon bioeconomic point of view compared with the use of fossil resources. This depiction embraces two key concepts, environmental sustainability and the sustainable development of technology for value-added products, including renewable biopolymers. The former is a significant part of current global climate change and the latter is involved with the development of greener technology for bio-based chemical products (Heo et al., 2019, Heo et al., 2020). In the assessment of environmental sustainability, the emissions of GHGs (greenhouse gases; carbon dioxide, methane, nitrous oxide, and fluorinated gases) function as a key indicator (EPA, 2018). In particular, CO₂ gas plays as the main contributor of GHG emissions (because ca. 81% of GHG is CO₂) (EPA, 2018). Several studies showed from the assessment of environmental sustainability that the use of raw biomass more favorably contributes to the reduction of GHG emissions (from 40 up to 60%, depending on feedstock type and processing system) compared with that of the reference process (IEA Bioenergy, 2019). As such, the use of raw biomass feedstocks is beneficial to the reduction of GHG emissions. In a case study, raw switchgrass for the production of HMF was used to examine the reduction effect of GHG emissions and as a result, a higher reduction of GHG emissions (up to 60%) was observed in its processing system compared with the use of fossil reference, depending on processing types (Heo et al., 2019). In another GHG balance analyses, two production processes of PEF from corn-based fructose and PET derived from fossil resource, both of which can be used as feeding substrates for the production of commodity plastics, were analyzed to compare the reduction efficiency of GHG emissions between them and as a result, the former showed 40–50% lower GHG/CO₂ emissions (Hwang et al., 2020; Jiang et al., 2020). The whole procedure of producing FDCA from raw biomass feedstocks is performed through a cascade processing step such as pretreatment of biomass feedstocks, their depolymerization to feed materials (e.g., fructose, glucose), and their dehydration to HMF, separation of intermediates (e.g., HMF), and HMF oxidation to FDCA (Fig. 2). In the direct conversion process of raw biomass feedstocks to FDCA, several processing steps can be eliminated. This elimination can significantly conduce to the reduction of GHG emissions as illustrated in Fig. 2.

From a techno-economic point of view, the direct conversion process of raw feedstocks to FDCA could conduce to the reduction of its production cost. The reason is, as mentioned above because several processing steps can be eliminated (Fig. 2). For example, the production processes of FDCA currently performed by the commercial venture companies are operated with HMF-based FDCA production technology (Table 1). However, its marketable production is not yet enough to produce it on an industrial scale due to the high production cost of HMF. Accordingly, the direct conversion process of raw biomass to FDCA could be significantly conducive to the cost-effective production of FDCA by skipping the costly processing steps (Fig. 2).

As such, the bio-based production process of FDCA is more favorable than the fossil-based process. Particularly, the direct conversion process of raw biomass feedstocks to FDCA is much more beneficial in both the environmental sustainability and bioeconomic points of view. However, there are concerns to be considered. These concerns include food security, disruption of biodiversity, land use, etc. Avoiding these concerns is a matter of great importance. One solution is to utilize non-food plant resources with no intensive systematic farming but capable of growing well in untapped land. Accordingly, the choice of biomass feedstock could be a significant factor for the sustainable development of FDCA production.

As another possible strategy conducible to reducing the cost of FDCA production from plant biomass feedstocks, the application of biomodification technology could be a useful approach. This technology would contribute to facilitating the production process and improving the content of target carbohydrates. As an example, inulin, which can be used as a useful substrate for FDCA production, can be genetically modified according to its application purpose. It is believed that the biomodification application would be a highly favorable approach for reducing the cost of FDCA production using raw plant biomass feedstocks.

The purpose of this review is to afford significant information on the sustainable technology for cost-efficient production of FDCA using inulin-rich raw plant biomass feedstocks by introducing some breakthrough approaches conducive to bio-based FDCA production. The discussion scopes include; the current technology trends of FDCA production, the importance of inulin polymer in producing FDCA, the discussion on plant sources with high content of inulin, new bioprocessing approaches for the direct oxidation of inulin rich raw plant feedstocks to FDCA, and biomodification strategies for enhancing the bioprocess efficiency and for improving the content of inulin in the targeted plant sources.