Effect of acid and alkaline on lignin degradation and enzymatic hydrolysis of cellulose in lignocellulosic wastes

Abstract EN

-Lignocellulosic wastes namely olive and tomato pomaces were treated with different concentrations and volumes of sulfuric acid, sodium hydroxide and ammonia at 25.

100 and 12IºC.

The lignin/cellulose (L/C), cellulose/lignin (C/L) ratios and the enzymatic hydrolysis of cellulose were used as indices for lignin degradation and cellulose availability for hydrolysis.

The highest lignin degradation with sulfuric acid was obtained with 0.5N at 12TC in 30 ml of the acid.

At this concentration the L/C ratio decreased from 0.36 to 0.23 and the C/L ratio increased from 2.8 to 4.4.

Treatment with 0.25N sulfuric acid at 100'C and 30 ml add volume resulted in 0.26 for L/C and 3.9 for C/L ratios.

No lignin degradation was observed with all acid concentrations at 25!C.

The highest lignin degradation with sodium hydroxide was obtained at 0.5N, 100°C in 40ml of the alkaline or at IN and 121ºC in 30ml alkaline: the L/C decreased from 0.36 to 0.21 and C/L increased from 2.8 to 4.9 in both treatments.

The other treatments either with sulfuric acid or sodium hydroxide gave lower delignification and cellulose availability than the above mentioned treatments.

The percentage of lignin degradation was 27.8% at 100 ºC and 36.1% at 121°C with sulfuric add.

while it was 41.4% with sodium hydroxide at both temperatures.

The highest enzymatic hydrolysis of cellulose in the olive pomace (98.3%) was obtained with samples pretreated with IN NaOH at 121 ºC.The maximum enzymatic hydrolysis (77.7%) was obtained with olive pomace pretreated with 10% aqueous ammonia at 121ºC.

The highest enzymatic hydrolysis of cellulose in tomato pomace was 94.3% obtained with treatment of tomato pomace with 0.5N NaOH at 12TC-While the maximum enzymatic hydrolysis of the tomato pomace (83.7%) obtained with 10% aqueous ammonia at 100 ºC.