Microwave Assisted Enzymatic Hydrolysis of Larch for L-Lactic Acid Production

Glucose production from pretreated larch by cellulose enzymatic hydrolysis with cellulase was investigated and compared with no pretreatment, as a reference. The larch was pretreated with microwave, sulfuric acid hydrolysis and dilute sodium hydroxide solution hydrolysis respectively. The cellulose material was also submitted to a pretreatment with dilute sodium hydroxide solution hydrolysis followed by microwave and with dilute sulfuric acid solution hydrolysis followed by microwave separately. The enzymatic hydrolysis experiments were carried out at 50°C, 50 g/l dry matter (DM) solid substrate concentration and 15 filter paper unit (IU)/g DM of a commercial cellulase. Fermentable sugar were able to be produced from all the pretreated larches with an overall yield of 10-30% of the maximum theoretical yield, based on the glucan available in the solid and liquid substrate. The larch pretreated with acid and microwave had the best yield as 30% followed by the larch pretreated with dilute sodium hydroxide solution with an overall yield of 18% with 15 IU/g DM of cellulase. Glucose was the main product with enzymatic hydrolysis yield ratio 11.74%in the sulfuric acid pretreated larch, while with enzymatic hydrolysis yield ratio 23.44%in the dilute sodium hydroxide solution pretreated larch under enzymatic hydrolysis conditions. These advantages, along with its negative price, make this solid a valuable raw material for L-lactic acid production.