**4.3 Biological methods**

Employing microorganism to pretreat lignocellulose is an attractive way, promising low cost in both equipment and operation expenses. *Pleurotus*, *Pycnoporus*, *Ischnoderma*, *Phlebia*, etc. have been cultivated on lignocellulose with expectation of utilizing the metabolism of the microorganism to destruct the crystallinity of cellulose and remove lignin. However, most studies were based on laboratory scales and showed limited results [26–29].

*Bioethanol Production from Lignocellulosic Biomass DOI: http://dx.doi.org/10.5772/intechopen.86437*

**Figure 4.**

*(a) SEM photo of rubber wood as starting material. (b) SEM photo of rubber wood pretreated by aqueous alkaline solution (2.0 wt.% NaOH for 24 h, the ratio of dry-biomass/solution was of 1/10 wt./wt.). (c) SEM photo of alkaline-pretreated rubber wood soaked in acidic solution for 24 h (2.0 wt.% H2SO4, the ratio of dry-biomass/solution was of 1/10 wt./wt.).*
