Synthesis of temperature and pH responsive lignin-grafted sulfobetaine for efficiently recycling cellulase

Recycling cellulase can reduce the cost of lignocellulosic enzymatic hydrolysis. Here, a lignin-grafted sulfobetaine (LSB) was first synthesized by grafting sulfobetaine (SB) on enzymatic hydrolysis lignin (EHL). LSB had a sensitive response of pH and temperature. LSB dissolved under the conditions of lignocellulosic enzymatic hydrolysis (pH 5.0, 50 degrees C). After hydrolysis, LSB co-precipitated with cellulase when lowering pH of the hydrolysate to 4.0 and cooling to 25 degrees C. When 3.0 g/L LSB-100 was added to the hydrolysis system of corncob residue (CCR), 70 % of amount of cellulase was saved. LSB had a remarkable response and stronger cellulase recovery capacity. This was attributed that carboxylate radical in LSB was protonated, and positive and negative ions of SB associated to form salt at 25 degrees C. This work provides a new idea for reducing the cost for preparing fermentable sugars from lignocellulose, and increasing the added value of EHL.

Automated summary

Recycling cellulase can reduce the cost of lignocellulosic enzymatic hydrolysis. A lignin-grafted sulfobetaine (LSB) was synthesized and showed a sensitive response to pH and temperature. LSB could be dissolved under the conditions of lignocellulosic enzymatic hydrolysis and co-precipitated with cellulase after hydrolysis, resulting in significant cellulase savings.