AUTHOR=Nawaz Ali , Qadoos Khadija , Haq Ikram Ul , Feng Yiwei , Mukhtar Hamid , Huang Rong , Jiang Kankan 

TITLE=Effect of pretreatment strategies on halophyte Atriplex crassifolia to improve saccharification using thermostable cellulases

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2023.1135424

DOI=10.3389/fbioe.2023.1135424

ISSN=2296-4185

ABSTRACT=<p>Bioethanol is believed to be an influential revolutionary gift of biotechnology, owing to its elevating global demand and massive production. Pakistan is home to a rich diversity of halophytic flora, convertible into bounteous volumes of bioethanol. On the other hand, the accessibility to the cellulosic part of biomass is a major bottleneck in the successful application of biorefinery processes. The most common pre-treatment procedures existent include physicochemical and chemical approaches, which are not environmentally benign. To overcome these problems, biological pre-treatment has gained importance but the drawback is the low yield of the extracted monosaccharides. The current research was aimed at exploring the best pre-treatment method for the bioconversion of halophyte <italic>Atriplex crassifolia</italic> into saccharides using three thermostable cellulases. <italic>Atriplex crassifolia</italic> was subjected to acid, alkali and microwave pre-treatments, followed by compositional analysis of the pre-treated substrates. Maximum delignification i.e. 56.6% was observed in the substrate pre-treated using 3% HCl. Enzymatic saccharification using thermostable cellulases also validated the results where the highest saccharification yield i.e. 39.5% was observed for the sample pre-treated using same. Maximum enzymatic hydrolysis of 52.7% was obtained for 0.40 g of the pre-treated halophyte <italic>Atriplex crassifolia</italic> where Endo-1,4-<inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">β</mml:mi></mml:mrow></mml:math></inline-formula>-glucanase (300U), Exo-1,4-<inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">β</mml:mi></mml:mrow></mml:math></inline-formula>-glucanase (400U) and <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">β</mml:mi></mml:mrow></mml:math></inline-formula>-1,4-glucosidase (1000U) were simultaneously added and incubated for 6 h at 75°C. The reducing sugar slurry obtained after optimization of saccharification was utilized as glucose in submerged fermentation for bioethanol production. The fermentation medium was inoculated with <italic>Saccharomyces cerevisiae,</italic> incubated at 30°C and 180 rpm for 96 h. Ethanol production was estimated using potassium dichromate method. Maximum production of bioethanol i.e. 16.33% was noted at 72 h. It can be concluded from the study that <italic>Atriplex crassifolia</italic> owing to its high cellulosic content after pre-treatment using dilute acid method, yields substantial amount of reducing sugars and high saccharification rates when subjected to enzymatic hydrolysis using thermostable cellulases, under optimized reaction conditions. Hence, the halophyte <italic>Atriplex crassifolia</italic> is a beneficial substrate that can be utilized to extract fermentable saccharides for bioethanol production.</p>