Bio-ethanol production from the shedding bark of Melaleuca leucadendron pretreated using Sub-critical water verses dilute acid was investigated.  The optimal pretreatment conditions were determined using a 4x3x3 factorial design. At very low severity conditions (CSF=0.335), 28% of xylan was recovered and this recovery increased with increasing CSF till it peaked to 64.4% (11.2 g xylose L-1) at a CSF of 1.475. However, at CSF >2.0, xylose yield declined due to degradation. The SEM images support the events, when increasing in CSF accompanied by the drop of the lengths and increasing of agglomeration and rougher surface of cellulose macrofibrils. Mild and progressive glucose yield was detected in prehydrolysate at CSF=1.514, and subsequent enzymatic hydrolysis allowed complete glucan solubilization. Implementing environmentally friendly subcritical water pretreatment at CSF=0.335, about 85% of glucan solubilization was achieved after enzymatic hydrolysis. Saccharomyces cerevisiae readily fermented crude hydrolysate with in 12 h, yielding 24.7 g L-1 ethanol at an inoculum size of 2% (v/v), representing a glucose to ethanol conversion rate of 0.475 g g-1 (93% fermentation efficiency). Based on our findings, the shedding bark is a potential feedstock for bio-ethanol production.

Subcritical water and dilute acid pretreatments for bio-ethanol production from Melaleuca leucadendron shedding bark

245th National Meeting (2013)

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