1. Introduction
The immoderate consumption of non-renewable energy, together with the fact that large urban areas, has greatly resulted in environmental deterioration and public health problems, has led to find a new renewable energy [1, 2]. Converting a renewable non-fossil carbon, such as energy crops and lignocellulosic residues (plants, grasses, fruit wastes and algae) to fuel would assure a continual energy supply [3]. Lignocellulosic material is the most abundant biopolymer on Earth and its annual production is estimated at approximately 50 billion tons [4]. Ethanol and hydrogen can be produced by microbial fermentations from such biomass [5]. However, the economics of biofuel production by fermentation are significantly influenced by the cost of the raw materials, which accounts for more than half of the production costs [6]. To achieve a lower production cost, the supply of cheap raw material is thus a necessity [1]. Pineapple waste, is the by-product of the canned pineapple, is a material rich in cellulose, hemicelluloses, sugar and other carbohydrates. These wastes consist of residual pulp, peels and skin. Canned pineapple has been one of Thailand’s main exports of canned fruit producer. The annual availability of these wastes amounts to 0.62 million tons [4]. The mechanical drying of these wastes gave opportunity to store the substrate all over the year [1].
Saccharomyces cerevisiae and Enterobacter aerogenes are the better known biofuel producing bacteria. E. aerogenes possesses advantage over S. cerevisiae respect to their ability to produce both ethanol and hydrogen under anaerobic condition. However, ethanol is produced commercially by S. cerevisiae because it ferments glucose to ethanol as a virtually sole product and it is known for its high ethanol tolerance, rapid fermentation rates and insensitivity to temperature and substrate concentration [1, 7].
The present investigation examined the production of ethanol and hydrogen from pineapple peel by S. cerevisiae TISTR 5048 and E. aerogenes TISTR 1468. High amount of reducing sugars in dried pineapple peel prompted us to make an attempt to utilize it as a raw material for biofuel production and develop of cheap medium. In addition, the immobilized cell technology was also investigated to increase biofuel production.