Microbe assisted depolymerization of lignin rich waste and its conversion to gaseous biofuel

Area of Science:

• Biotechnology
• Renewable Energy
• Biorefining

Background:

• Lignocellulosic ethanol production generates lignin-rich residue (LRR).
• Valorizing LRR is crucial for biorefinery efficiency and circular economy principles.
• Effective lignin depolymerization is key to unlocking LRR's energy potential.

Purpose of the Study:

• To evaluate the biomethanation potential of LRR after microbe-assisted pretreatment.
• To assess the efficiency of lignin-depolymerizing consortia (LDC) in breaking down lignin.
• To integrate biomethanation with ethanol fermentation for enhanced energy conversion.

Main Methods:

• Selective enrichment of lignin-depolymerizing consortia (LDC).
• Microbial pretreatment of LRR, alkali lignin (AL), and dealkali lignin (DL) using LDC.
• Assessing LDC efficiency via lignin breakdown, enzyme activity, and dye decolorization.
• Biomethanation of pretreated substrates to determine biogas yield.
• Evaluating energy conversion efficiency.

Main Results:

• LDC treatment significantly degraded lignin: LRR (46.33%), AL (31.37%), DL (34.20%).
• Microbial pretreatment of LRR resulted in a higher biogas yield (424 ml/g VS).
• Pretreated commercial lignins also yielded substantial biogas (302-324 ml/g VS).
• An additional energy conversion efficiency of 11.75 kJ/g VS was achieved.

Conclusions:

• LRR from lignocellulosic ethanol fermentation is a viable feedstock for biomethanation.
• Integrating biomethanation with ethanol fermentation enhances energy recovery and closes the biorefinery loop.
• This approach supports the circular economy and addresses gaseous fuel demands.