The degradation of cellulose by an anaerobic and thermophilic bacterium Clostridium thermocellum ATCC 27405, was studied. It has been found that this organism is able to convert cellulose directly to ethanol and other chemicals including sugars. The specific growth rate of this organism on Solka Floc was about 0.05 $hr^{-1}$. The final concentration of the accumulated reducing sugars was 3.4 g/liter representing a 58% accumulation of the degraded cellulose (5.84 g/liter).
The ability of Cl. thermocellum to grow on glucose depends on yeast extract concentration : glucose was utilized in the medium containing 5g to 7g yeast extract per liter. When it was again transferred to cellulose medium, it retained the ability to utilize cellulose. When it was cultivated in the glucose medium containing 0.5% yeast extract, cell growth was observed after a lag of 30 hr to 35 hr and the specific growth rate was about 0.16$hr^{-1}$. The cellulolytic activity was expressed also in the glucose medium.
Among the growth factors studied, biotin showed the most pronounced effect on glucose utilization and the effect of thiamine HCl was a little less than biotin. Riboflavin showed no effect.
When both glucose and cellobiose were present in the medium containing 0.5% yeast extract, the culture utilizes cellobiose preferentially without an extended lag, but the glucose-adapted culture assimilated glucose preferentially without an extended lag.
The glucose-adapted culture grew in the glucose medium containing 0.2% yeast extract.
When Cl. thermocellum was cultivated on cellobiose, cellobiose was degraded and accumulated glucose. During active growth phase, the mole ratio of the accumulated glucose to the degraded cellobiose was less than one. But after cell growth was terminated, the mole ratio was between one and two.
In case of the glucose-adapted culture, the specific growth rate of this culture on Solka Floc was about 0.155$hr^{-1}$ and 55% of cellulose was degraded. In addition, the accumulated reducing sugars was only 16% of the degraded cellulose (5.2 g/liter).
In case of the mixed population, the specific growth rate was about 0.177$hr^{-1}$ and 52% of the cellulose was degraded. But no reducing sugars from cellulose were accumulated.
혐기성 고온성 세균인, Clostridium thermocellum ATCC 27405에 의한 섬유소의 분해가 연구되었다. 이 세균은 섬유소를 직접에탄올과 당류를 포함한 다른 화학물질로 전환할수 있음이 알려졌다.
이세균의 Solka Floc에 대한 특이성장속도는 약 0.05 $hr^{-1}$ 였다. 축적환원당의 최종농도는 3.4g/liter 였고, 이것은 분해된 섬유소(5.84g/liter)의 58%가 축적됨을 나타냈다.
Cl. thermocellum의 포도당에 대한 성장능력은 효모추출물의 농도에 의존한다. 즉 포도당은 5~7g/ℓ의 효모추출물을 포함하는 배지에서 사용되었다. 다시 섬유소배지에 옮겼을 때, 섬유소의 이용능력이 유지되었다.
0.5% 효모추출물을 포함하는 포도당배지에 배양했을때 세포성장은 30~35 시간 후에 관찰되었고 특이성장속도는 약 0.16 $hr^{-1}$ 였다. 섬유소분해활성도는 포도당배지에서도 나타났다.
연구된 성장인자들 중, biotin은 포도당이용에 대해 가장 큰 효과를 보였고, $Vit.B_1$의 효과는 biotin 보다 약간 적었다. 반면에 $Vit. B_2$는 전혀 효과가 없었다.
포도당과 섬유이당이 0.5% 효모추출물을 포함한 배지에 동시에 존재했을때, 배양균은 섬유이당을 먼저 이용하나, 포도당적응성 배양균은 포도당을 먼저 이용하였다.
포도당적응성 배양균은 0.2% 효모추출물을 포함한 포도당배지에서 성장하였다.
Cl. thermocellum을 섬유이당에 배양했을때, 섬유이당은 분해되고 포도당이 축적되었다. 성장이 활발한 시기에는 분해된 섬유이당에 대한 축적된 포도당의 몰비율이 1보다 적었다.
그러나 균성장이 멈춘후, 그몰비율은 1과 2 사이였다.
포도당적응성 배양균인 경우, Solka Floc에 대한 특이성장속도는 약 0.155 $hr^{-1}$였고 55%의 섬유소가 분해되였다. 뿐만아니라, 축적환원당은 분해된 섬유소의 16%에 불과했다.
혼합배양인 경우, 특이성장속도는 약 0.177 $hr^{-1}$였고 섬유소의 52%가 분해되었다. 그러나 환원당은 전혀 축적되지 않았다.
