Improvement of Nicotine Removal and Ethanol Fermentability From Tobacco Stalk by Integration of Dilute Sulfuric Acid Presoak and Instant Catapult Steam Explosion Pretreatment.

Hongsen Zhang,Guotao Mao,Fengqin Wang,Tianbao Ren,Zhimin Wang,Andong Song,Hui Xie,Chenqing Fu

doi:10.3389/fbioe.2021.763549

Hongsen Zhang, Guotao Mao + Show 6 more

Open Access

https://doi.org/10.3389/fbioe.2021.763549

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Abstract

The nicotine from tobacco stalk showed obvious inhibitory effect on the activity of cellulase and fermentability of microorganisms, which seriously hinders the utilization of tobacco stalk. Dilute sulfuric acid presoak of tobacco stalk was used to enhance the performance of instant catapult steam explosion (ICSE) for tobacco stalk pretreatment. The presoak was beneficial to break the recalcitrant structure of tobacco stalk, reduce nicotine content to relieve the inhibition on the activity of cellulase and metabolism of microorganisms, and promote the performance of enzymatic hydrolysis and ethanol fermentation. The optimized 0.8% sulfuric acid (w/w) presoak–integrated ICSE pretreatment resulted in 85.54% nicotine removal from tobacco stalk; meanwhile, the total sugar concentration from enzymatic hydrolysis of pretreated tobacco stalk increased from 33.40 to 53.81 g/L (the ratio of dry tobacco stalk to water was 1:8, w/w), ethanol concentration increased 103.36% from 5.95 to 12.10 g/L in flask, compared with separate ICSE pretreatment. Finally, the ethanol concentration achieved the highest 23.53 g/L in a 5-L fermenter with the ethanol yield from the glucose of tobacco stalk hydrolysate achieving 71.40% by increasing the solid loading of the tobacco stalk in the enzymatic hydrolysis process (the ratio of dry tobacco stalk to water was 1:4, w/w). These results achieved the expected purpose of efficient utilization of discarded tobacco stalk.

Highlights

With the vigorous development of the world economy, the environment pollution and nonrenewable resources consumption have become a severe challenge to the human society; more and more attention has been focused on new renewable and environment-friendly energy; and relevant research has become a mainstream of scientific community (Herbert and Krishnan, 2016)
Three substrates were used to study the effects of nicotine on the activity of cellulase which was always used in biomass hydrolysis processes
Cellulase activity was characterized by carboxymethyl cellulase (CMC) activity and filter paper cellulase activity (FPA), and the results showed that the activity of cellulase decreased gradually with the increase of nicotine concentration (Figure 1)

Summary

Introduction

With the vigorous development of the world economy, the environment pollution and nonrenewable resources consumption have become a severe challenge to the human society; more and more attention has been focused on new renewable and environment-friendly energy; and relevant research has become a mainstream of scientific community (Herbert and Krishnan, 2016). As a clean and renewable energy, bioethanol showed many significant advantages such as being green and Tobacco Stalk for Ethanol Production environment-friendly, having low manufacturing cost, having wide availability, and so on (Zhou et al, 2019). Nicotine is the main alkaloid of tobacco, which accounts for over 95% of the total alkaloid content of tobacco (Henry et al, 2019). Nicotine is both an addictive and a toxic substance, which can inhibit the activity of biological enzymes and the growth of microorganisms, and can go against tobacco stalk efficient utilization (Swanson et al, 1994; Zhong et al, 2010; Falco and Bevins, 2015). Instant catapult steam explosion (ICSE) has become an efficient, economic, and environmental pretreatment technology, depending on its short pretreatment time, low energy consumption, and zero pollution to the environment (Wang et al, 2020; Xie et al, 2020)

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