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. 2022 Feb 4;23(3):1777.
doi: 10.3390/ijms23031777.

Role of Combined Na2HPO4 and ZnCl2 in the Unprecedented Catalysis of the Sequential Pretreatment of Sustainable Agricultural and Agro-Industrial Wastes in Boosting Bioethanol Production

Shaimaa Elyamny  1 , Ali Hamdy  2 , Rehab Ali  3 , Hesham Hamad  3
Affiliations

Role of Combined Na2HPO4 and ZnCl2 in the Unprecedented Catalysis of the Sequential Pretreatment of Sustainable Agricultural and Agro-Industrial Wastes in Boosting Bioethanol Production

Shaimaa Elyamny et al. Int J Mol Sci. .

Abstract

Improper lignocellulosic waste disposal causes severe environmental pollution and health damage. Corn Stover (CS), agricultural, and aseptic packaging, Tetra Pak (TP) cartons, agro-industrial, are two examples of sustainable wastes that are rich in carbohydrate materials and may be used to produce valuable by-products. In addition, attempts were made to enhance cellulose fractionation and improve enzymatic saccharification. In this regard, these two wastes were efficiently employed as substrates for bioethanol production. This research demonstrates the effect of disodium hydrogen phosphate (Na2HPO4) and zinc chloride (ZnCl2) (NZ) as a new catalyst on the development of the sequential pretreatment strategy in the noticeable enzymatic hydrolysis. Physico-chemical changes of the native and the pretreated sustainable wastes were evaluated by compositional analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). These investigations showed major structural changes after the optimized sequential pretreatment. This pretreatment not only influences the delignification process, but also affects the functionalization of cellulose chemical structure. NZ released a higher glucose concentration (328.8 and 996.8 mg/dl) than that of ZnCl2 (Z), which released 203.8 and 846.8 mg/dl from CS and TP, respectively. This work led to the production of about 500 mg/dl of ethanol, which is promising and a competitor to other studies. These findings contribute to increasing the versatility in the reuse of agricultural and agro-industrial wastes to promote interaction areas of pollution prevention, industrialization, and clean energy production, to attain the keys of sustainable development goals.

Keywords: Tetra Pak; ZnCl2; bioethanol production; corn stover; enzymatic hydrolysis; fermentation; functionalization; phosphate; pretreatment; waste recycling.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic description of the pretreatment steps for Tetra Pak (TP) and Corn Stover (CS) to produce Tetra Pak and corn stover treated by ZnCl2 (TPZ) and (CSZ), and Tetra Pak and Corn Stover treated by Na2HPO4 then ZnCl2 (TPNZ) and (CSNZ) respectively, for enzymatic hydrolysis and subsequently for bioethanol production.
Figure 2
Figure 2
Solid recovery, cellulose recovery, and lignin removal of the two substrates under the different pretreatments.
Figure 3
Figure 3
Produced glucose from enzymatic hydrolysis and bioethanol liberated after fermentation of the hydrolysate.
Figure 4
Figure 4
SEM images of (a) TP, (b) TPZ, (c) TPNZ, (d) CS, (e) CSZ, and (f) CSNZ.
Figure 5
Figure 5
FTIR spectra of (a) TP and (b) CS, before and after pretreatment.
Figure 6
Figure 6
Acidic groups of TP and CS samples, before and after pretreatment.
Figure 7
Figure 7
XRD of (a) TP and (b) CS, before and after pretreatment.
Figure 8
Figure 8
(a) TGA and (b) DTG of TP, TPZ, and TPNZ.
Figure 8
Figure 8
(a) TGA and (b) DTG of TP, TPZ, and TPNZ.
See this image and copyright information in PMC

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