Comprehensive understanding of the effects of metallic cations on enzymatic hydrolysis of humic acid-pretreated waste wheat straw

Abstract

Background Humic acids (HA) have been used in biorefinery process due to its surfactant properties as an aid to the pretreatment of lignocellulose, with results indicating a positive effect on delignification. However, the HA remaining on the surface of the pretreated lignocellulose has also been shown to provide a negative effect on ensuing enzymatic digestibility. Hence, a strategy of complexing metallic cations with HA prior to enzymatic hydrolysis was proposed and demonstrated in this work in an effort to provide a means of HA mitigation that does not involve significant water consumption via extensive washing. Results Results showed that the enzymatic hydrolysis efficiency of waste wheat straw decreased from 81.9% to 66.1% when it was pretreated by 10 g/L HA, attributed to the inhibition ability of the residual HA on enzyme activity of cellulase with a debasement of 36.3%. Interestingly, enzymatic hydrolysis efficiency could be increased from 66.1% to 77.3% when 10 mM Fe3+ was introduced to the system and allowed to associate with HA during saccharification. Conclusions The addition of high-priced metallic cations (Fe3+) has successfully alleviated the effect of HA on cellulase activity. It is our hope in demonstrating the complexation affinity between metallic cations and HA, future researchers and biorefinery developers will evaluate this strategy as a unit operation that could allow economic biorefining of WWS to produce valuable biochemicals, biofuels, and biomaterials.

Recent advances in understanding the effects of lignin structural characteristics on enzymatic hydrolysis

“…Lignocellulose is rich in cellulose (40–50%) along with hemicelluloses (20–30%) and lignin (15–30%) [ 1 ]. The linear cellulose and branched hemicelluloses are the main polysaccharides for green biofuels production via biorefinery technology [ 2 , 3 ]. However, the presence of lignin in the cell walls confers rigidity to the lignocellulose, which prevents the structural polysaccharides from degradation by microorganisms and enzymes (Fig.…”

Study on the Flocculation Performance of a Cationic Starch‐Based Flocculant on Humic Substances in Textile Dyeing Wastewater

“…In addition to the various variables mentioned above, the presence of inorganic salts can also affect the final flocculation results. [ 64,65 ] The effect of inorganic salt on the flocculation performance of St‐g‐PDMC, CPAM, and PAC were investigated in HA solution with mass fraction of 80 mg L −1 , T = 25 °C and t = 45 min. In order to investigate the effect of inorganic salt concentration and its charge concentration on flocculation performance, we chose LiCl, NaCl, MgCl 2 , CaCl 2 , and AlCl 3 .…”

Effect of surfactant addition on disperser disintegration of water hyacinth: a new insight to overcome the inhibitory effects of lignin on methanogenesis and improve the energy and economic aspects

“…The two main constituents that contribute majorly to biofuel production in lignocellulosic biomass are celluloses and hemicelluloses. 4,5 Water hyacinth biomass (WHB) (Eichhornia crassipes) is regarded as one of the best biomass sources that can be utilized as a substrate for biomethanation. WHB is a free-oating aquatic macrophyte found in stagnant water systems.…”

“…The two main constituents that contribute majorly to biofuel production in lignocellulosic biomass are celluloses and hemicelluloses. 4,5…”