**4.1 Oil palm trunk**

The huge biomass output of the oil palm trunk (OPT) has piqued the interest of researchers. OPT has a 25 to 30 years average active life period [19]. The OPT is usually chopped into small pieces and left to rot naturally in the plantation area during the replanting period. Leaving the trunk in the plantation area may cause pollution because the OPT's high sugar and starch content will attract microflora and microfauna, raising the risk of plant diseases [20].

When compared to the other sections of oil palm trees, OPT sap contains liquid with a lower lignin percentage and a higher percentage of free fermentable sugars [20]. As a result, there is little to no need for pre-treatment (chemical or biological) to delignify or convert lignocellulose to fermentable sugar. **Table 3** lists the different biochemical products that are made with OPT as a substrate. The product's differences are mainly determined by the type of microorganisms used and the fermentation conditions (i.e. temperature, pH, oxygen level).


#### **Table 3.**

*Biochemical products from different organisms using OPT as substrate.*
