Tamarind extract pretreatment: Valorization of sugarcane bagasse for cellulase production by <i>Aspergillus flavus</i>

Abstract

Effective pretreatment is crucial for cellulase production from sugarcane bagasse. Pretreatment with tamarind extract could reduce the hazardous effect associated with chemical pretreatment. The present work investigated tamarind (Tamarindus indica) extract in combination with H₂SO₄ and thermal pretreatment of sugarcane bagasse for cellulase production by Aspergillus flavus. The sugarcane bagasse was pretreated with tamarind extract pH 2 and pH 4, followed by 1% H₂SO₄ and thermal treatment at 121°C for 15 min. The pretreatment slurry was analysed for reducing sugar while solid bagasse was analysed for weight loss. Aspergillus flavus grew on sugarcane bagasse under solid state fermentation and the Carboxy Methyl Cellulase (CMCase) and Filter Paper Assay (FPA) activities were compared on the various pretreatments. The pretreatments changed the visible morphology of the sugarcane bagasse observed by the swelling, fibrous appearance and colour change. Pretreatment slurry yielded highest soluble reducing sugar at 60.01 mg/ml in tamarind extract (pH 4/1% H₂SO₄ ) and highest weight  loss of solids at 73.70% in tamarind extract (pH 2/1% H₂SO₄ /thermal 121°C). Aspergillus flavus performed better on tamarind extract (pH 2/1% H₂SO₄ ) by producing optimal CMCase and FPA activities at 0.100 U/ml and 0.409 U/ml respectively after 3 days of fermentation. Cellulase was maximally active at temperature of 50 °C. The tamarind extract pretreatment successfully proved to be an alternative organo-chemical pretreatment of sugarcane bagasse as evidenced by the physical properties, soluble reducing sugars and cellulase activities.

Keywords: Aspergillus flavus, Cellulase, Pretreatment, Sugarcane bagasse, Tamarind extract