Overcoming challenges for the biorefineries of the future

Moirangthem, Kamaljit (2017) Overcoming challenges for the biorefineries of the future. PhD thesis, University of Nottingham.

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Non-food lignocellulosic biomass is the most abundantly available raw material. Utilising it for biorefinery purposes not only circumnavigates the food vs fuel debate, but is also important for a complete move to a fossil fuel free society. Some of the major challenges in using lignocellulosic feedstock includes its recalcitrance, potential shortage for year-round mono feedstock supply and economic viability with current technology.

The first part of this thesis explores the potential of overcoming recalcitrance of wheat straw by exploiting new wheat back cross (BC1) plants, which were developed at Nottingham, using introgression of genes from wild relatives, with the aim to improve wheat genetic variation. The straw from a subset of 128 BC1 were screened for sugar content and saccharification efficiency. Plants showed wide compositional and structural differences, reflecting a high degree of genetic diversity. The digestibility of the stem tissue was assessed following acid hydrothermal pre-treatment and a significant variation was detected. This demonstrated that this approach to wheat breeding was successful in introducing a wide range of phenotypic, compositional and structural changes and digestibility into the wheat straw.

The second part of the thesis aimed to address the potential bottle neck in mono-feedstock availability in a biorefinery, as most lignocellulosic feedstocks are likely to be seasonal. One way to overcome this may be by utilising a mixed feedstock to maintain a year-round supply. This study reports the impact of mixing three of the UK’s most important feedstocks- wheat straw, willow and Miscanthus on two major performance indicators - sugar yield and fermentation inhibitor production. A hot water pre-treatment regime of 200°C for 5 minutes was applied to each feedstock individually and to 1:1 (w/w) mixes and the predicted sugar yield in the mixes was compared to the observed values. All the mixes resulted in improved sugar yields with willow + Miscanthus and wheat + willow showing a statistically significant improvement over predicted values. Inhibitor production during the pre-treatment and its impact on yeast metabolism and growth were also compared and no adverse impacts of mixing observed. The use of mixed feedstocks in a hot water based commercial production of biofuels is unlikely to have any adverse effects on productivity and may indeed prove beneficial.

The final part of the thesis, explores the potential of combining extraction of a high value product (anthocyanin) from black rice - Chakhao poireiton straw, followed by use of the residual straw for saccharification for an economical biorefinery.
The anthocyanin content of black rice straw, as determined by standard methanol extraction, was 62.8±4.2 mg/100g. Aqueous microwave treatment at 90°C for 5 minutes extracted 85.8% of this anthocyanin and importantly the extract then displayed higher antioxidant capacity compared to methanol extracts. Extracts showed negligible cytotoxicity, or induction of apoptosis, on Jurkat cell lines even at high concentrations (200-800μg/ml). The straw residue after anthocyanin extraction showed a glucose digestibility of 49.67±1.4% after a subsequent pre-treatment at 200 °C for 5 minutes.
This study demonstrates the potential to develop a combined biorefinery process for anthocyanin and second-generation sugars using black rice straw as the feedstock

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Tucker, Gregory
King, Julie
King, Ian
Keywords: Black rice straw, wheat straw, Miscanthus, Willow, Biofuel, High value products, Biorefinery, Anthocyanin, Lignocellulose
Subjects: T Technology > TP Chemical technology > TP 368 Food processing and manufacture
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 48138
Depositing User: Moirangthem, Kamaljit
Date Deposited: 18 Apr 2018 13:41
Last Modified: 06 May 2020 12:17
URI: https://eprints.nottingham.ac.uk/id/eprint/48138

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