2019 Volume 65 Issue 1 Pages 25-32
For utilization of various biomass such as herbaceous tissue or leaves, a rapid and suitable lignin determination method is required. Here, we report a modification of the thioglycolic acid (TGA) method for rapid determination of lignin content in various samples. Our data demonstrated that 1 h instead of 16 h is enough to extract TGA lignin by NaOH, and no time but inverting is required to precipitate TGA lignin by concentrated HCl, indicating that the incubation time of the TGA method can be reduced from 23 h to 4 h. Lignin content in various samples determined by this rapid TGA (rTGA) method using absorbance at 280 nm was the same as with the conventional method. Furthermore, lignin obtained by the rTGA method was freeze-dried and weighed. This gravimetry of the rTGA (grTGA) method determined lignin content almost identical to that obtained with the Klason method in wood samples. Lignin contents of Japanese cedar leaves determined by the grTGA and Klason methods were 16.2% and 37.8%, respectively. The Wiesner reaction revealed that leaves of Japanese cedar have limited lignified tissue, suggesting that the grTGA method is more suitable for determining lignin in leaves. The grTGA method requiring no standard curve may be a rapid lignin determination method applicable to a wide variety of samples.
