Research On Hydrogen Production By Thermoanaerobacterium Thermosaccharolyticum W16 Immobilized On Biological Carrier

Bio-hydrogen production is considered as clean and economic gaseous fuel for the future. Although, the rate of fermentative hydrogen production is always faster than photosynthetic, it is still too low for commercial exploitation. This problem can be overcome by developing some suitable microorganism with high hydrogen production capability and also by improvement of cell density through whole cell immobilization. In order to enhance biomass retention and hydrogen productivity in continuous process, the immobilized whole cell technique should be developed. The major problems of these carriers used for the immobilization were high cost, few immobilized biomass and low substrate conversion efficiency. There are also some deficiencies in stability, mechanical properties and immobilized effect. In order to obtain a higher cell density and biological activity in immobilization process, it is necessary to develop a new type of immobilized carrier. Environmentally friendly biological carrier such as mycelia pellet was chosen as immobilization supports in this study. Mycelia pellet is a kind of bio-granule formed spontaneously in the process of Aspergillus niger Y3 fermentation. An important advantage of the mycelia pellet morphology is the filamentous in porous and large surface area, resulting in improved mixing and mass transfer properties. It is also beneficial to the adhesion of the bacteria. In addition, it has a short generation time, good biological activity,rapid propagating, and low production costs.Possibilities of using biological mycelia pellet as carrer for immobilization of Thermoanaerobacterium thermosaccharolyticum W16 are explored for enhancing the production of hydrogen. Various immobilization parameters of mycelia pellets dosage, mycelia pellets size and culturing time were firstly carried out to determine their levels affecting hydrogen production and glucose utilization, and subsequently response surface methodology (RSM) was adopted to investigated the optimum value of these factors for achieving maximum hydrogen yield. Under these conditions, continuous hydrogen production with immobilized cells in continuous stirred-tank reactor (CSTR) was further investigated. At a dilution rate of 0.0775h-1 and stirring rate 200rpm/min, It obtained that the accumulation of hydrogen was up to 6292 mL with immobilized cells which was 8.7% higher than the culture obtained by carrier-free. The buffering properties of hydrogen production reator with biological carrier accelerated the start-up period, H2 production rate achieved 98.39mLH2/L h during stablely operating period which was 17.8% higher than the data of 83.91mLH2/L h derived from free cells, biomass was also maintained at 0.6960g/L ~ 0.8157g/L higher than 0.6413g/L ~ 0.7754g/L obtained by carrier-free.