TABLE 2.

Examples of interactions between cellulolytic and noncellulolytic microorganisms in defined mixed culture

Cellulolytic organismNoncellulolytic organismSubstrateCultivation methodEffects of coculturingReference
Clostridium thermocellumMethanobacterium thermoautotrophicumMCCa cellobioseBatch, 60°CIncreased rate of cellulose degradation; end product shifts from ethanol to CH4 (via H2); interspiecies H2 transfer uncoupled at high growth rate on cellobiose737
C. thermosaccharolyticumSolka FlocBatch, 60°C3-fold increase in ethanol production rate484
C. thermohydrosulfuricumSteam-expl., aspen2-fold decrease in ethanol production rate; decreased soluble sugar accumulation
C. thermohydrosulfuricumCelluloseIncreased rate of cellulose degradation; relief of yeast extract requirement through cross-feeding of vitamins and methionine467
C. thermosaccharolyticumSolka floc, corn stoverBatch, 60°CIncreased ethanol selectivity719
Fibrobacter succinogenesSelenomonas ruminantiumCelluloseBatch, 39°CUtilization of cellulose fragments by S. ruminantium, conversion of succinate to propionate by S. ruminantium598
Ruminococcus albusMethanobrevibacter smithiiMCCContinuous, 37°CMethanogenesis via interspecies H2 transfer at all dilution rates; no measurable change in cellulose conversion or cell yield518
F. succinogenes or Ruminococcus flavefaciensPrevotella ruminicolaOrchardgrass or alfalfaBatch, 38°CExtent of cellulose digestion increased in some cocultures193
F. succinogenes or Buytrivibrio fibrisolvensTreponema bryantiiBarley strawBatch, 39°CIncrease rate and extent of digestion of barley straw but not of pure cellulose361
Trichoderma harzianumClostridium butyricumCellulose (undescribed)BatchProducts of aerobic cellulose hydrolysis used by anaerobic, N2-fixing Clostridium712
Cellulomonas flavigenaAzospirillum brasilenseFilter paper, wheat strawBatch, 30°CPhysical association observed between cellulose degrader and N2-fixing Azospirillum239
Cellulomonas flavigenaXanthomonas sp.Alkaline-treated bagasseContinuous, 30-40°CHigher μmax in coculture than in either monoculture540
  • a MCC, microcrystalline cellulose.