Yeast hardening for cellulosic ethanol production
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Yeast Hardening for Cellulosic Ethanol production. Bianca A. Brandt Supervisor: Prof J Gorgens Co-Supervisor: Prof WH Van Zyl Department of Process Engineering University of Stellenbosch. Energy Postgraduate Conference 2013. Introduction.

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Yeast hardening for cellulosic ethanol production

Yeast Hardening for Cellulosic Ethanol production

Bianca A. Brandt

Supervisor: Prof J Gorgens

Co-Supervisor: Prof WH Van Zyl

Department of Process Engineering

University of Stellenbosch

Energy Postgraduate Conference 2013


Introduction

Introduction

  • Growing global move towards sustainable green energy production

    • spurred by dependence on rapidly depleting finite fossil fuels

    • environmental and socio-economic concerns

  • Studies into Alternative Clean, Renewable and Sustainable energy resources:

    • solar-electric/thermal, hydroelectric, geothermal, tidal, wave, wind and ocean thermal power systems

    • furthermore, a great deal of work has gone into the development of biofuels


Introduction1

Introduction

  • Why Biofuels?

    • vehicular transportation- energy stored easier in form of combustible hydrocarbons then as electricity or heat

    • compatible with current distribution systems

    • supplement and replace fossil fuels

  • A range of bio-fuels are currently being investigated

  • Bioethanol - benchmark biofuel

    • production based on a proven low cost technological platform

    • Brazil and USA - cost effective 1st generation bioethanol

    • sugar and starch

  • 2nd generation bioethanol from lignocelluloses


Cellulosic bioethanol

Cellulosic Bioethanol

  • Bioethanol from Lignocellulose

    • cheap, renewable, easily available, under utilized resource

    • energy/fuel and suitable molecules which can replace petroleum products

  • Lignocellulose bioethanol production process

    • degradation of lignocellulose to fermentable sugars

    • fermentation of sugars to bioethanol

  • Optimum ethanol production bottle necked

    • suboptimal xylose utilization and release of microbial inhibitor molecules during biomass degradation

Fermentation

Pretreatment

Hydrolysis


Overcoming inhibitor toxicity

Overcoming Inhibitor toxicity

  • Challenge – Release of inhibitor molecules during lignocellulose degradation

    • furans, phenolics and weak acids

    • severely impact yeast fermentation efficiency

  • Process Optimization

    • feedstock, pretreatment, hydrolysis conditions

    • fermentation strategies

  • Detoxification of hydrolysate

    • physical (evaporation); chemical (over-liming)

    • biological: microbial and enzymatic approaches

  • Shown detoxification costs can constitute 22% of total ethanol production cost (Ding et al., 2009)

    • economically limited

    • inhibitor specific and loss of fermentable sugars


Overcoming inhibitor toxicity1

Overcoming Inhibitor toxicity

  • Sustainable cost effective bioethanol fermentation require “hardened” inhibitor resistant fermentation strains

  • Rational engineering approach

    • Genetic modification – yeast oxido-reductase detoxification genes

    • boost innate detoxification mechanisms of yeast

    • furfural, HMF, Formic acid

    • improved tolerance to specific inhibitor

  • Evolutionary engineering techniques

    • mutation and long term continuous cultures

    • simulate natural selection under selective pressure


Hardening yeast

Hardening yeast

  • Despite on-going yeast hardening strategies

  • Inhibitor resistant fermentation strains remain elusive and highly sought after!!

  • Project aim : Generate “hardened” inhibitor resistant yeast strains

  • Approach which combine Novel rational metabolic engineering and evolutionary engineering


Hardening yeast1

Hardening yeast

  • Strain generation - Rational metabolic engineering

    • industrial xylose utilization base strains

  • Identify and select yeast detoxification genes from literature

    • combine specific detoxification genes with cell membrane stress response genes

  • Express inhibitor resistance genes in Saccharomycescerevisiae

    • novel gene combinations

    • elucidate synergistic /antagonistic combinations


Hardening yeast2

Hardening yeast

  • Evolutionary engineering

    • long term continuous cultures - bioreactor

    • selective pressure – increasing concentrations of inhibitors

    • further enhance inhibitor resistance

    • evaluate fermentation efficiency in toxic hydrolysate

  • Novel “HARDENED” inhibitor resistant strains

  • Optimization of lignocellulosic bioethanol production


Acknowledgements

Acknowledgements

Supervisors: Prof J Gorgens and Prof WH Van Zyl

Department of process engineering

NRF - Financial Support

Thank You


Yeast hardening for cellulosic ethanol production

Yeast Hardening for Cellulosic Ethanol production

Bianca A. Brandt

Supervisor: Prof J Gorgens

Co-Supervisor: Prof WH Van Zyl

Department of Process Engineering

University of Stellenbosch

Energy Postgraduate Conference 2013


Introduction2

Introduction

  • Growing global move towards sustainable green energy production

    • Spurred by dependence on rapidly depleting Finite Fossil fuels

    • Various environmental and socio-economic concerns

  • Studies into Alternative Clean, Renewable and Sustainable energy resources:

    • solar-electric/thermal, hydroelectric, geothermal, tidal, wave, wind and ocean thermal power systems

    • furthermore, a great deal of work has gone into the development of bio-fuels


Introduction3

Introduction

  • Why Biofuels?

    • Vehicular transportation- energy stored easier in form of combustible hydrocarbons then as electricity or heat

    • compatible with current distribution systems

    • Supplement and replace fossil fuels

  • A range of bio-fuels are currently being investigate

  • Bioethanol - benchmark biofuel

    • production based on a proven low cost technological platform

    • Brazil and USA -cost effective 1st generation bioethanol

    • Sugar and starch

  • 2nd generation bioethanol from lignocelluloses


Cellulosic bioethanal

Cellulosic Bioethanal

  • Bioethanol from Lignocellulose

    • cheap, renewable, easily available, under utilized resource

    • energy/fuel and suitable molecules which can replace petroleum products

  • Lignocellulose bioethanol production process

    • degradation of lignocellulose to fermentable sugars

    • fermentation of sugars to bioethanol

  • Optimum ethanol production bottle necked

    • suboptimal xylose utilization and release of microbial inhibitor molecules during biomass degradation

Fermentation

Pretreatment

Hydrolysis


Overcoming inhibitor toxicity2

Overcoming inhibitor toxicity

  • Challenge – Release of inhibitor molecules during lignocellulose degradation

    • furans, phenolics and weak acids

    • severely impact yeast fermentation efficiency

  • Process Optimization

    • feedstock, pretreatment, hydrolysis conditions

    • fermentation strategies

  • Detoxification of hydrolysate

    • physical (evaporation); chemical (over-liming)

    • biological: microbial and enzymatic approaches

  • Shown detoxification costs can constitute 22% of total ethanol production cost (Ding et al., 2009)

    • economically limited

    • inhibitor specific and loss of fermentable sugars


Overcoming inhibitor toxicity3

Overcoming inhibitor toxicity

  • Sustainable cost effective bioethanol fermentation require “hardened” inhibitor resistant fermentation strains

  • Rational engineering approach

    • Genetic modification – yeast oxido-reductase detoxification genes

    • boost innate detoxification mechanisms of yeast

    • furfural, HMF, Formic acid

    • improved tolerance to specific inhibitor

  • Evolutionary engineering techniques

    • mutation and long term continuous cultures

    • simulate natural selection under selective pressure


Hardening yeast3

Hardening yeast

  • Despite on-going yeast hardening strategies

  • Inhibitor resistant fermentation strains remain elusive and highly sought after!!

  • Project aim : Generate “hardened” inhibitor resistant yeast strains

  • Approach which combine Novel rational metabolic engineering and evolutionary engineering


Hardening yeast4

Hardening yeast

  • Strain generation - Rational metabolic engineering

    • Industrial xylose utilization base strains

  • Identify and select yeast detoxification genes from literature

    • Combine specific detoxification genes with cell membrane stress response genes

  • Express inhibitor resistance genes in Saccharomyces cerevisiae

    • novel gene combinations

    • elucidate synergistic /antagonistic combinations


Hardening yeast5

Hardening yeast

  • Evolutionary engineering

    • long term continuous cultures - bioreactor

    • selective pressure – increasing concentrations of inhibitors

    • further enhance inhibitor resistance

    • evaluate fermentation efficiency in toxic hydrolysate

  • Novel “HARDENED”inhibitor resistant strains

  • Optimization of lignocellulosic bioethanol production


Acknowledgements1

Acknowledgements

Supervisors: Prof J Gorgens and Prof WH Van Zyl

Department of process engineering

NRF - Financial Support

Thank You


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