Potential of corn cobs for production of biofuels and biochemicals

Corn cobs, which are available in large quantities in the continental Croatia, were subject of this work because they can be used as a readily available, renewable lignocellulosic feedstock for biotechnological production of biofuels, biochemicals and many other products. The effect of alkaline treatment on corn cobs composition was investigated, using gravimetric and spectrophotometric analytical methods. Portions of dry matter, ash, protein, extractive substances, lignin and cellulose were analysed in the starting raw material and compared with those obtained after treatment with sodium hydroxide. The results obtained for corn cobs were generally in line with the values reported in the literature, while minor deviations can be interpreted as the influence of genetic factors, growing conditions, modes of production and storage as well as the impact of the applied analytical methods. Portion of total lignin in the dry matter of corn cobs was 11.55 % (10.02 % and 1.54 % of insoluble and soluble lignin, respectively). The share of total extract in dry matter of corn cobs after alkaline treatment was 1.26 % (0.53 % of water extract and 0.73% of ethanol extract). This treatment has removed a large part of lignin. The treated corn cobs contained 5.19 % of the total lignin (2.46 % and 2.73 % of insoluble and soluble lignin, respectively) in the dry matter. At the same time there has been an increase of the portion of cellulose in the dry matter, with approximately 42.23 % in the raw material to 74.38 % in the alkaline treated feedstock. Portion of hemicellulose, calculated by subtracting other compounds from the total solids, were 39.00 and 18.52 % for corn cobs and alkaline treated feedstock, respectively. Numeric indicators, applicable for comparison of variations in raw materials, as well as for monitoring of lignocellulose pretreatments and solid-state fermentation, have also been introduced in this work.