Characterization Of The Cadmium Accumulation With Wheat Straws That Distinctively Affects Cell Wall Composition And Bioethanol Production

Cadmium?Cd?as a major hazardous substance,has been examined to pollute partial agricultural land.Phytoremediation is a powerful technology for Cd removal based on crop straw accumulation with Cd.Meanwhile,crop straw provide enormous biomass residues for biofuels and other chemical production.However,much remains unknown about the optimal pretreatment technology for both high bioethanol production and complete Cd collection with relatively less secondary pollution to the environment.In this study,we collected three mature straws of wheat cultivars that were grown in soil pots co-supplied with Cd,and examined the maximum Cd accumulation,determined their cell wall compositions and major wall polymer features.Meanwhile,we tested biomass enzymatic saccharification and bioethanol production under chemical pretreatment.We proposed a mechanistic model elucidating how the Cd accumulation distinctively affected cell wall compositon and features for largely enhanced lignocellulose enzymatic saccharification and bioethanol production.The main results were described as follows:1.Mutant?ZT5?showed much increased Cd accumulation in the straw than those of the wild type?WT?and mutant?ZT7?.On the other hand,all straw tissues contained significantly more Cd than those of the grain.2.Supplied with Cd in the soil pots,all wheat samples showed significantly reduced cellulose and pectin levels,with reduced rates of 5.13%¹1.55% and 5.48%¹2.85%.However,all wheat samples did not show significantly altered hemicellulose and lignin levels compared to the control?without Cd supplement?.3.Supplied with Cd in the soil pots,three wheat samles showed significantly increased soluble sugars levels by 23.08%¹42.41%.4.Compared with the raw materials,the two-step?0.5%NaOH+2%H₂SO₄? pretreated residues led to significantly reduced cellulose DP,but it caused much increased lignocellulose porosity and cellulose surface accessibility,which may integrate to affect sequential lignocellulose saccharification.5.Supplied with Cd,three wheat samples showed much increased bioethanol yields by 3.96%¹6.78%,compared to the controls?without Cd suply?.6.Two-step pretreatments?0.5%NaOH+2%H₂SO₄?with two wheat straws led to 98%?of total?Cd release,whereas the one-step pretreatment?2%H₂SO₄ or 4% NaOH?only caused 67%⁸7%Cd release.