Effect of microwave‐assisted alkali pre‐treatment on fractionation of pistachio shell and enzymatic hydrolysis of cellulose‐rich residues

Abstract

BACKGROUNDPistachio shell is a lignocellulosic biomass with a high potential to be converted into chemicals, biopolymers, and biofuels. Alkaline pre‐treatment is an effective way to extract hemicellulose and increase the cellulose hydrolysis. However, there are some disadvantages to this process, such as a long processing time and the formation of high amounts of degradation products. Microwave irradiation can be used to enhance the effectiveness of alkaline treatment. In this study, microwave‐assisted alkali pre‐treatment (MAAP) was carried to fractionate pistachio shell into its valuable components (i.e., hemicellulose and cellulose), and the enzymatic hydrolysis of cellulose‐rich residues was performed to produce fermentable sugars.RESULTSThe MAAP conditions (microwave power, NaOH concentration, and pre‐treatment time) were studied and optimized by Box–Behnken design to obtain the highest hemicellulose and cellulose yields. Optimal pre‐treatment conditions were microwave power of 224 W, NaOH concentration of 1.96 N, and pre‐treatment time of 2.63 min. Under these conditions, the recoveries were 58.35% and 92.46% for hemicellulose and cellulose, respectively. Additionally, compositional analysis carried out on the solid and liquid fractions obtained from the pre‐treatments indicated that the main components in the liquid phases were xylooligosaccharides (XOS) and the solid phases were enriched in cellulose. MAAP enhanced the enzymatic hydrolysis yield, and a maximum glucan to glucose conversion yield of 82.67 mol% was obtained for the solid pre‐treated under optimum conditions.CONCLUSIONThe studied MAAP process could be an effective and viable option to extract hemicellulose from pistachio shell and increase the enzymatic digestibility of cellulose‐rich solid residues. © 2020 Society of Chemical Industry (SCI)

The green novel approach in hydrolysis of pistachio shell into xylose by microwave‐assisted high‐pressure CO2/H2O

“…Hemicellulose, cellulose and lignin compositions in pistachio shell were found to be 461.3, 245.0 and 248.3 g kg −1 respectively. The results were comparable with the previously reported results in the literature 34,35 . Total hemicellulose content (376.0 g kg −1 xylan and 85.3 g kg −1 acetyl groups) was found to be two‐fold higher in the present study compared to that of obtained by Okutucu et al 36 .…”

Microwave-assisted cassava pulp hydrolysis as food waste biorefinery for biodegradable polyhydroxybutyrate production

“…Overall, as shown in Table 2 , the irradiation power and time play the most important role in the internal thermal effect which is generated by the direct interaction between the heated material and electromagnetic field in microwave heating, and consequently producing rapid and volumetric heating ( Özbek et al, 2021 ). In addition to the thermal effects of microwave, the non-thermal effects also provide a physical explosion effect within the microfibers, which speed up the breakdown of the resistant lignocellulosic structure.…”

Valorization of sawdust biomass for biopolymer extraction via green method: Comparison with conventional process

“…In this context, although several synthesis methods have been proposed to separate cellulosic compounds. The chemical methods are still the most used because there is no special requirements as well as they can be operated at low temperatures 47,48 . By comparing the chemical methods, it has been stated that typical Kraft pulping process requires many operation steps with water, sodium sulfide (Na 2 S), NaOH, and bleaching with free‐ or based‐methods 49 ; whereas simple alkaline treatment has the advantage of requiring inexpensive chemicals, processing in mild conditions and high efficiency in lignin and xylan removal with minimal sugar degradation 49 .…”