Tuesday, May 3, 2011
There is a growing interest in the valorization of lignocellulosic biomass within the biorefinery framework. The biochemical approach has been used in many studies for these purpose, however it requires the selective biomass fractionation. Dilute-acid hydrolysis is being widely used, as it can provide pentose-rich hydrolyzates that can be used for the preparation of culture media to produce added-value products. However, in addition to sugars, some toxic compounds are also produced which decreases the bioprocess productivity. These toxic compounds can be divided into 4 groups: aliphatic acids, furan derivates, phenolic compounds, and metallic ions. In order to remove these, several detoxification methods such as, overliming, activated charcoal, or ion-exchange resins, have been successfully applied, although they all have some limitations. The development of a new detoxification method based on flocculation employing tannin-based biopolymers may be an advantage, due to its biodegradability, antimicrobial properties, and low cost.
In this work, two inexpensive proprietary tannin-based biopolymers were tested for the detoxification of sugar cane bagasse hemicellulosic hydrolyzate. The effects of biopolymer concentration, pH, temperature and contact time were studied using a 2^4 experimental design for both biopolymers. The results revealed that pH and concentration are the most significant factors and these were further studied for both polymers. Under optimized conditions it is possible to selectively remove phenolics (>80%), furans (>57%), and metallic ions (54-99%) with minimal sugar removal (<5%), which compares favorably to other methods, making this an interesting alternative for hydrolyzates detoxification.