Infrared spectroscopy analysis of hemp (Cannabis sativa) after selective delignification by Bjerkandera sp at different nitrogen levels

Fourier-transform infrared F-IR) spectroscopy has been used to monitor chan ges in C/N-modified lignocellulosic substrates from Cannabis sativa L, in a 7-week solid-state fermentation with the white-rot fungus Bjerkandera sp, strain BOS55. The microbial transformation of hemp was considered as a pret reatment to pulping processes in paper industries. Special emphasis was pai d on the N-content of the substrate, which was modified by: (i) external am monium inputs, (ii) water extraction, and (iii) protease treatment. Selective delignification in the N-limited media was observed. The most dia gnostic FT-IR spectral bands in relation to changes in the lignocellulosic substrate were those corresponding to alkyl structures (2920, 1460 cm(-1)), carboxyl groups (1720 cm(-1)), amides (1650, 1540 cm(-1)) and carbohydrate (mainly 1030 cm(-1)). Simple and multiple regression functions revealed th e potential of FT-IR in accurately reflecting substrate composition feature s previously determined by wet chemical methods. Correspondence analysis su ggests C/N-dependent degradation patterns, and discriminant analysis confir med that the differences between N-limited, N-enriched and the original sub strate were significant (P < 0.05) in terms of the intensities of five FT-I R diagnostic bands (1030, 1130, 1270, 1540 and 1650 cm(-1)). The results suggest that, in the system studied, the FT-IR spectroscopy is a reliable alternative to wet chemical analyses in the routine monitoring o f the success of the biologic process since it reflects both qualitative an d quantitative changes and it is very sensitive to lignin alteration and to carbohydrate and protein concentration. (C) 2001 Elsevier Science Inc. All rights reserved.