Delignification of Aloe Vera Rind by Mild Acid Associated Microwave Pretreatment to Persuade Enhanced Enzymatic Sacchari
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SHORT COMMUNICATION
Delignification of Aloe Vera Rind by Mild Acid Associated Microwave Pretreatment to Persuade Enhanced Enzymatic Saccharification Gunasekaran Rajeswari1 · Balakrishnan Arutselvy1 · Samuel Jacob1 Received: 10 May 2019 / Accepted: 23 September 2019 © Springer Nature B.V. 2019
Abstract Aloe vera rind (AVR), a discarded solid biomass after extraction of gel finds no commercial importance could serve as a potent lignocellulosic feedstock for bioethanol production that prerequisite an efficient pretreatment to remove the lignin (16.4%, w/w). In the present study, the impact of mild acid pretreatment on AVR by using microwave energy with varied power (160 W, 320 W and 480 W) and its efficiency on saccharification was evaluated. Microwave acid pretreatment resulted in threefold decrease in recalcitrant lignin (5.58%, w/w) at 480 W than untreated AVR biomass. The effect of pretreatment on AVR biomass was characterized by various analytical techniques. X-Ray Diffraction (XRD) patterns deciphered an increase in cellulose crystallinity (14.8%) of delignified AVR biomass as compared to raw biomass (10.5%) and the extent of structural distortion after pretreatment was clearly indicated by Scanning Electron Microscopy (SEM). Fourier-Transform Infra-Red (FTIR) spectra revealed the disappearance of peak around 1241 cm−1 (C–O stretching) indicated the deacetylation of hemicellulose after pretreatment. Gas Chromatography Mass Spectrometry (GC–MS) analysis of liquid hydrolysate obtained after pretreatment unveiled the presence of higher fraction of carboxylic acids, esters, aromatic and aliphatic hydrocarbons as a result of lignin oxidation. The maximum reducing sugar obtained by crude cellulase from the delignified AVR biomass was found to be 296.8 ± 1.26 mg/g as compared to untreated AVR biomass (129.68 ± 2.34 mg/g). This study has shown the acid microwave pretreatment of AVR biomass could effectively improve the yield of fermentable sugars that are further used for ethanol production. Graphic Abstract
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12649-019-00830-7) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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Waste and Biomass Valorization
Keywords Aloe vera rind · Delignification · Enzymatic saccharification · Microwave-mild acid pretreatment · Reducing sugars · Lignin degradatory by-products
Statement of Novelty Through this study, Aloe vera rind a prominent waste from aloe gel processing industries is established as a potent feedstock for bioethanol production through a hybrid pretreatment strategy i.e., Microwave assisted mild acid pretreatment is reported for the first time. Further, conversion of the holocellulosic components to reducing sugars were carried using a locally isolated cellulase producer that is identified as Aspergillus sp. The hydrolysate and the degradatory byproducts upon analysis by GC–MS were found to contai
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