Designing whole cells for bio-transformation of lignin derived aromatics
Suveera. V. Bellary, Aruna Mahesh, Arvind.M.Lali
DBT-ICT Centre for Energy Biosciences, Institute of Chemical Technology, Nathalal Parakh Marg
Matunga, Mumbai-400099
Email address: shrutakka_b@yahoo.com, arunamahesh32@gmail.com, arvindmlali@gmail.com
1. Introduction
Lignin, a principal component of lignocellulosic biomass is unexploited primarily due to
its inherent heterogeneity and complex structure. The valorization of lignin along with
polysaccharide to products of commercial importance will improve the economics of biorefinery. Chemical treatment of lignin leads to myriad slate of aromatic molecules. The
aromatic species obtained can be selectively bio-transformed by microbes to single
products making the process environmentally benign and easy for separation. This
research entails mining of microbes to bio-catalyze the aromatics obtained from lignin.
2. Materials and Methods
Vanillin, trans-p-coumaric acid, syringaldehyde, BSTFA: TMCS (99:1) was procured
from Sigma Aldrich. Syringic acid, vanillic acid, ferulic acid was purchased from SD
Fine Chemicals. Pyridine was obtained from Lobachemie.
Growth profile was studied using aromatic monomers as sole carbon source
supplemented with mineral salts. Metabolic profiling was carried out using HPLC with
Methanol: Water: Acetic Acid (25:74:1) as mobile phase. The products formed were also
analyzed using GC-MS after derivatization.
3. Results and Discussions
3.1 Chemical treatment of biomass primarily gives rise to mixture of aromatics which
consists of Vanillin, vanillic acid, syringaldehyde, syringic acid, benzoic acid and transp-coumaric acid
Trans-pCoumaric acid
Syringaldehyde
Vanillic acid
Vanillin
Syringate
Benzoic
acid
Fig 1: GC-MS chromatogram of biomass-pretreated liquor containing aromatics
3.2 Growth and metabolic profile of microbes: The aromatics present in the liquor
were used individually and in combination to study growth
Growth profile on mixture of Vanillin, Vanillic acid,
Syringaldehyde and Syringic acid
0.35
O.D at 600 nm
0.3
0.25
Pseudomonas putida
KT2440
0.2
0.15
Pseudomonas putida S12
0.1
Pseudomonas putida
isolate
0.05
0
0
50
100
150
Time(hrs)
Fig 2: Growth profile of strains on mixture of aromatics (1mM each)
Pseudomonas putida KT 2440 was unable to utilize syringic acid and syringaldehyde
despite being a known strain for biotransformation of aromatic compounds. Therefore
Pseudomonas putida S12 and isolate Pseudomonas putida were studied. Tolerance study
was also performed on each aromatic and both the strains can sustain concentrations up to
15mM. Metabolic profiling was carried out to ascertain the intermediates generated
during catabolism of these compounds. Both the strains are able to utilize lignin derived
compounds without having any inhibitory effect.
4. Conclusion The two Pseudomonas strains possessing complete aromatic catabolic
potential are being evaluated for their bio-catalytic capabilities on lignin stream and can
be further subjected to genetic engineering for synthesis of value added products.
5. References
[1]Salvachua et al, Towards Lignin consolidated bioprocessing- Simultaneous lignin
depolymerization and product generation by bacteria, Green Chemistry, RSC Publishing,
June 2015
[2]Linger et al, Lignin valorization and through integrated biological funneling and
chemical catalysis, PNAS, August 2014, 12013-12018
[3]Wang et al. Connecting lignin degradation pathway with pre-treatment inhibitor
sensitivity of Cupriavidus necator. Frontiers in Microbiology, May 2014.