Anotace:
The study aimed to develop a novel bioprocessing protocol for lignocellulose conversion into ethanol without the use of any chemical for pre-treatment. The feedstock, mature sweet sorghum bagasse, was milled and sieved to 40 and 80 mesh (physical treatment) to have samples with particle size of 0.425 mm and 0.180 mm, respectively. After which, samples were inoculated with either single or co-culture of P. ostreatus and T. harzianum (biological) for 28 days followed by sonication (mechanical) with varying time duration. The effectivity of the different treatments under each protocol was evaluated based on delignification and saccharification of the biomass complex via spectrophotometric standard analytical procedure. Cellulose-derived glucose was inoculated with S. cerevisiae under anaerobic conditions to assess its fermentability. Testing of the different treatment combinations was conducted at 5g substrate while the best treatment combination was validated at both 5g and 100g levels. Independent optimization trials of the different treatments showed the significant effect of smaller particle size of 0.180 mm, co-culture of P. ostreatus and T. harzianum, and sonication time of 20 min in improving the delignification and saccharification efficiencies of the sweet sorghum biomass. These parameters were combined together as one protocol (physico-bio-mechanical). Saccharification efficiency of this protocol under the 5g scale is ±10.67% against ±9.96% at 100g-scale. This is a big leap compared to the ±3.0-5.0% obtained in our previous experiment. Ethanol yield obtained from the same condition were 2.73%w/w and 1.77%w/w for the 5g and 100g-scale, respectively. It can be confidently stated here, that the present study is the first to ever produce cellulosic ethanol at laboratory-scale condition without chemical pre-treatment.