Floriotis, G.

Gavala, Hariklia N.

Haugen, T.

Heggeset, T. M. B.

Le, S. B.

Markussen, S.

V. Skiadas, Ioannis

Varrone, Cristiano

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Nov 08, 2017The glycerol Biorefinery: Valorization of crude glycerol through its conversion intobiofuels and green chemicals by mixed microbial consortiaVarrone, Cristiano; Floriotis, G. ; Heggeset, T. M. B.; Le, S. B. ; Haugen, T.; Markussen, S.; Skiadas,Ioannis V; Gavala, Hariklia N.Published in:Book of Abstracts. DTU's Sustain Conference 2015Publication date:2015Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Varrone, C., Floriotis, G., Heggeset, T. M. B., Le, S. B., Haugen, T., Markussen, S., ... Gavala, H. N. (2015). Theglycerol Biorefinery: Valorization of crude glycerol through its conversion into biofuels and green chemicals bymixed microbial consortia. In Book of Abstracts. DTU's Sustain Conference 2015 [R-4] Lyngby: TechnicalUniversity of Denmark (DTU).	  	  	  The	  glycerol	  Biorefinery:	  Valorization	  of	  crude	  glycerol	  through	  its	  conversion	  into	  biofuels	  and	  green	  chemicals	  by	  mixed	  microbial	  consortia	  	  C.	  Varrone1*,	  G.	  Floriotis1,	  T.	  M.	  B.	  Heggeset2,	  S.	  B.	  Le,	  T.	  Haugen2,	  S.	  Markussen2,	  I.	  V.	  Skiadas1	  and	  H.N.	  Gavala1.	  1DTU	  Chemical	  Engineering;	  2	  SINTEF	  Materials	  and	  Chemistry.	  *Corresponding	  author	  email:	  cvar@kt.dtu.dk	  In	   recent	  years,	   the	  exponential	  growth	  of	  biodiesel	  production	  has	   led	   to	  concomitant	   increase	   in	  crude	  glycerol	  (CG).	  Even	  though	  pure	  glycerol	  represents	  a	  valuable	  product	  for	  the	  cosmetic	  and	  pharmaceutical	  industry,	   CG	   from	   biodiesel	   production	   is	   contaminated	  with	   compounds	   such	   as	   salts,	  methanol,	   soap,	  long	  chain	   fatty	  acids,	  etc.	  These	  contaminants	  cause	  high	  purification	  costs	  when	  converting	  glycerol	  by	  traditional	   chemico-­‐physical	  methods.	   Thus,	   the	  use	  of	   anaerobic	   fermentation	   to	   convert	   abundant	   and	  low-­‐priced	  glycerol	  streams	  generated	   in	  the	  production	  of	  biodiesel	   into	  higher	  value	  products	  has	  been	  proposed	   as	   a	   promising	   route	   to	   achieve	   economic	   viability	   in	   the	   biofuels	   industry	   1.	   However,	   most	  studies	  on	  glycerol	  fermentation	  so	  far	  have	  been	  focusing	  mainly	  on	  the	  use	  of	  purified	  glycerol	  and	  pure	  cultures,	  while	  typically	  observing	  reduced	  yields	  and/or	  productivities	  when	  testing	  CG2.	  The	  objective	  of	  this	  study	  was	  thus	  to	  select	  and	  adapt	  mixed	  microbial	  consortia	  (MMC)	  directly	  on	  CG,	  targeting	  MMC	  able	  to	  produce	  biofuels	  (hydrogen	  and	  ethanol)	  and/or	  green	  chemicals	  (i.e.	  VFAs	  and	  1,3	  propanediol).	   Various	   adaptation	   strategies	   were	   investigated	   for	   the	   enrichment	   of	   suitable	   and	   stable	  MMC,	   trying	   to	   overcome	   inhibition	   problems	   and	   enhance	   substrate	   degradation	   efficiency,	   as	   well	   as	  generation	  of	  soluble	  fermentation	  products.	  Moreover,	  different	  CG	  types	  were	  tested,	  including	  CG	  from	  animal	   fat	   derived	   (second-­‐generation)	   biodiesel2,3.	   Repeated	   transfers	   in	   small	   batches	   and	   fed-­‐batch	  conditions	   have	   been	   applied,	   comparing	   the	   use	   of	   different	   inocula	   (different	   origin	   and	   thermal	   pre-­‐treatment),	  growth	  media	  and	  kinetic	  control,	  while	  continuous	  stirred	  tank	  reactor	  (CSTR)	  operations	  have	  been	   established	   to	   test	   the	   effect	   of	   pH	   and	   hydraulic	   retention	   time	   (HRT).	   Changes	   in	   microbial	  composition	  were	  monitored	  by	  means	  of	  Next	  Generation	  Sequencing	  technique,	  revealing	  a	  dominance	  of	  glycerol	   consuming	   species,	   such	  as	  Clostridium,	  Klebsiella	   and	  Escherichia3.	  Our	  previous	  experiments	  with	  biofuels	  production	  showed	  the	  possibility	  to	  reach	  a	  yield	  of	  >	  0.9	  mol	  H2/mol	  Gly	  and	  1	  mol	  EtOH/mol	  Gly4,	   in	   non-­‐sterile	   conditions	   and	   without	   nutrient	   supplements5.	   We	   are	   now	   going	   to	   start	   a	   new	  investigation	  targeting	  the	  process	  intensification,	  by	  means	  of	  gas-­‐stripping	  removal	  of	  ethanol,	  cell	  mass	  recirculation,	  as	  well	  as	  optimization	  of	  microaerophilic	  conditions	  to	  enhance	  ethanol	  production.	  	  Regarding	  green	  chemicals,	  1,3	  propanediol	  turned	  out	  to	  be	  the	  dominant	  metabolite	  in	  most	  of	  the	  cases	  (maximum	  yield	  of	  0.52	  g/g),	  followed	  by	  butyrate.	  Maximum	  butyrate	  production	  yield	  reached	  around	  0.4	  g/g	  (with	  10	  g/L	  substrate),	  but	  stabilized	  at	  around	  2	  g/g	  during	  the	  steady	  state.	  Substrate	  (≈10	  g/L)	  was	  completely	  consumed	  during	  CSTR	  experimentation	  (with	  only	  one	  exception),	  and	  no	  ethanol	  production	  was	  observed,	  while	  reaching	  a	  maximum	  of	  0.46	  g	  EtOH/g	   in	  batch3.	   Interestingly,	   the	  same	  phenomenon	  was	  observed	  also	  with	  the	  MMC	  optimized	  for	  ethanol	  production.	  In	  general,	  different	  inoculum	  sources	  requested	  different	   approaches,	   but	  were	   able	   to	   be	   acclimatized	   to	   the	  diluted	   (also	   fat-­‐derived)	   crude	  glycerol,	   without	   the	   need	   of	   any	   costly	   pretreatment	   of	   the	   feed.	   Ongoing	   work	   is	   now	   focusing	   on	  identification	  of	  the	  operating	  parameters	  for	  maintaining	  a	  stable	  MMC	  and	  statistical	  optimization	  of	  key	  parameters	  for	  enhanced	  green	  chemicals	  production.	  	  	  References:	  1)	  	  Yazdani,	  S.	  S.	  &	  Gonzalez,	  R.	  Curr.	  Opin.	  Biotechnol.	  18,	  213–9	  (2007).	  	  	  	  2)	  Varrone,	  C.	  (Patent)	  PCT/IT2012/000281;	  International	  Publication	  Number:	  WO	  2013/038435	  A1.	  (2013).	  	  	  	  3)	  Varrone,	  C.	  et	  al.	  Biomed	  Res.	  Int.	  1–14	  (2015).	  	  	  4)	  	  Varrone,	  C.	  et	  al.	  Int.	  J.	  Hydrogen	  Energy	  37,	  16479–16488	  (2012).	  	  5)	  	  Varrone,	  C.	  et	  al.	  Appl.	  Energy	  105,	  349–357	  (2013).	  	  Sustain DTU Abstract: R-4

The glycerol Biorefinery: Valorization of crude glycerol through its conversion into biofuels and green chemicals by mixed microbial consortia

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The glycerol Biorefinery: Valorization of crude glycerol through its conversion into biofuels and green chemicals by mixed microbial consortia

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