Soft Microwave Pretreatment to Extract P-Hydroxycinnamic Acids from Grass Stalks

Abstract

The aim of this article is to provide an analysis of microwave effects on ferulic and coumaric acids (FA and CA, respectively) extraction from grass biomass (corn stalks and miscanthus). Microwave pretreatment using various solvents was first compared to conventional heating on corn stalks. Then, microwave operational conditions were extended in terms of incident power and treatment duration. Optimal conditions were chosen to increase p-hydroxycinnamic acids release. Finally, these optimal conditions determined on corn stalks were tested on miscanthus stalks to underlie the substrate incidence on p-hydroxycinnamic acids release yields. The optimal conditions—a treatment duration of 405 s under 1000 W—allowed extracting 1.38% FA and 1.97% CA in corn stalks and 0.58% FA and 3.89% CA in miscanthus stalks. The different bioaccessibility of these two molecules can explain the higher or lower yields between corn and miscanthus stalks.

Microwave Pretreatment of Lignocellulosic Biomass to Release Maximum Phenolic Acids

“…PAyield = (PAliberated in soluble content mg/g) / (PAinitial mg/g) equation [5] From Table 1 we can see that phenolic acids extraction significantly increased when PMW treatment was employed (p = 0.00755); FA extraction yield is more than ten times higher than in Ctest, which is consistent with the previous parietal composition analysis. In the case of C + treatment, FA extraction yield reached 94%, which confirms the theory of almost complete extraction of FA by NaOH.…”

“…Based on previous works [5], optimal conditions for extracting phenolic acids were determined. Alkaline water (pH = 8.5 obtained by adding 6.7 mmol NaOH to 200 ml water), S/L ratio 1:21 (w:w), total volume of 200ml, incident power of 500W, treatment duration of 270s and high stirring were determined as adequate conditions to extract phenolic acids.…”

“…Phenolic acids were quantified in the raw biomass and the obtained values were the following: 4.2mg FA/g DM and 13.1mg pCA/gDM. Extraction yields in the liquid and pvalues were calculated using equation [5] and results are summed up in Table 1.…”

Material utilization of green waste: a review on potential valorization methods

“…From the leaves a yield of approximately 2% wax was obtained, containing long-chain hydrocarbons, fatty acids, n-policosanols, aldehydes, wax esters, sterols, and steroid ketones (Attard et al2016). Bichot et al pretreated Miscanthus with microwaves and extracted 0.6% ferulic acid and 3.9% coumaric acid (Bichot et al 2019). According to Karlen et al, extraction titers of at least 50 g kg −1 biomass are necessary to make the extraction of hydroxycinnamic acids economically feasible (Karlen et al 2020).…”

Accessing p‐Hydroxycinnamic Acids: Chemical Synthesis, Biomass Recovery, or Engineered Microbial Production?

“…[68][69][70][71][72][73] However, enzymatic hydrolyses were also actively investigated (e. g., Table 4, entries 1 and 2). [74][75][76][77][78][79][80] Extractions by PLE, [81,82] microwave, [83,84] or extrusion [83] were explored, but their efficiency appears limited, probably due to the encasement of ferulic and p-coumaric acids in the matrix of plant cells (Table 4, entries 3 and 4). To overcome this limitation, reductive catalytic fractionation (RCF) on herbaceous feedstock can be an alternative to cleave both ether and ester linkages.…”