Chicken feather and wheat straw hydrolysate for direct utilization in biobutanol production

Abstract

Lignocellulosic material possesses a source of fermentable saccharides for biofuel production, however it must be supplemented with other nutrients for microbial growth. We have investigated the use of chicken feather as a source of amino acids and peptides. Alkaline hydrolysis of feather under mild conditions (80 °C, 0.6% NaOH) provided a highly solubilized preparation of assimilable nitrogen. Similar conditions were applicable for pre-treatment of wheat straw. The concentration of lignocellulose-derived inhibitors was low so washing or detoxification steps were unnecessary. Therefore, hydrolysis of both materials was carried out simultaneously, resulting in a cultivation medium that was suitable for direct use in biobutanol production. Thirteen strains of solventogenic clostridia were tested for their ability to produce butanol on this mixed hydrolysate; strains of Clostridium beijerinckii and Clostridium saccharoperbutylacetonicum produced the highest butanol concentrations. The proposed process of simultaneous hydrolysis followed by direct inoculation was then demonstrated by experimental production of butanol in a laboratory bioreactor, using C. beijerinckii strain NCIMB 8052 and producing 4.6 g/L of butanol. Although process optimization is still required, we have shown that feather and wheat straw could be co-processed, forming a convenient mixed substrate for biobutanol production.