TABLE 2.

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

Cellulolytic organismNoncellulolytic organismSubstrateCultivation methodEffects of coculturingReference
Clostridium thermocellum Methanobacterium thermoautotrophicum MCCa 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 cellobiose 737
C. thermosaccharolyticum Solka FlocBatch, 60°C3-fold increase in ethanol production rate 484
C. thermohydrosulfuricum Steam-expl., aspen2-fold decrease in ethanol production rate; decreased soluble sugar accumulation
C. thermohydrosulfuricum CelluloseIncreased rate of cellulose degradation; relief of yeast extract requirement through cross-feeding of vitamins and methionine 467
C. thermosaccharolyticum Solka floc, corn stoverBatch, 60°CIncreased ethanol selectivity 719
Fibrobacter succinogenes Selenomonas ruminantium CelluloseBatch, 39°CUtilization of cellulose fragments by S. ruminantium, conversion of succinate to propionate by S. ruminantium 598
Ruminococcus albus Methanobrevibacter smithii MCCContinuous, 37°CMethanogenesis via interspecies H2 transfer at all dilution rates; no measurable change in cellulose conversion or cell yield 518
F. succinogenes or Ruminococcus flavefaciens Prevotella ruminicola Orchardgrass or alfalfaBatch, 38°CExtent of cellulose digestion increased in some cocultures 193
F. succinogenes or Buytrivibrio fibrisolvens Treponema bryantii Barley strawBatch, 39°CIncrease rate and extent of digestion of barley straw but not of pure cellulose 361
Trichoderma harzianum Clostridium butyricum Cellulose (undescribed)BatchProducts of aerobic cellulose hydrolysis used by anaerobic, N2-fixing Clostridium 712
Cellulomonas flavigena Azospirillum brasilense Filter paper, wheat strawBatch, 30°CPhysical association observed between cellulose degrader and N2-fixing Azospirillum 239
Cellulomonas flavigena Xanthomonas sp.Alkaline-treated bagasseContinuous, 30-40°CHigher μmax in coculture than in either monoculture 540
  • a MCC, microcrystalline cellulose.