Production of enzymes from underutilised crops using biological pretreatment

Knight, Siobhan Megan (2017) Production of enzymes from underutilised crops using biological pretreatment. MPhil thesis, University of Nottingham.

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A rapidly growing demand for food, feed, fuel and fibre has put a strain on vital resources, leading to increased concern of energy security. This, along with threats of global warming has attracted research into renewable energy sources and the development of new technologies for biofuel and biochemical production. The use of lignocellulosic material for the production of sustainable and cost-effective value-added products could offer a solution, with underutilised crops playing an important role as the raw material used in the biorefining process. However, enzymatic hydrolysis of the lignocellulosic material is one of the major barriers to an economically viable process, preventing its widespread application.

The aim of this research was to investigate the feasibility of using solid state fermentation (SSF) of underutilised crops for the generation of cellulase and glucoamylase enzymes and fermentable sugars, providing the basis for a biorefining process for converting the crops to bioethanol and/or biochemicals.

Several underutilised crops were investigated – Bambara, Leucaena, Napier grass, Nipa palm, Oil palm fronds, and Sago hampas. Characterisation of the crops was performed to determine their basic composition. The crops were screened to investigate which crop(s) had the highest potential as a substrate for fungal cellulase production during SSF and submerged fermentation (SmF). Two fungi, Aspergillus niger and Trichoderma reesei, were used, exploring different fermentation conditions to optimise the process. The use of A. niger during SSF resulted in the highest cellulase activity overall. Under baseline conditions (addition of deionised water to 80% (w/v) moisture content (MC)), the cellulase activity after five days of incubation ranged from 1.08 ± 0.06 FPU/g to 17.17 ± 0.44 FPU/g, with the use of Napier resulting in the highest activity. This activity was increased significantly with the addition of starch (0.0070 g/g), yeast extract (YE, 0.0175 g/g) and minerals. When these nutrients were added to Napier, the cellulase activity increased to as high as 31.02 ± 1.01 FPU/g.

Since Sago hampas contained over 50% (w/w) starch, it was also investigated as a substrate for the production of fungal glucoamylases and fermentable sugars, using the fungus A. awamori. Glucoamylases could not be detected in SSF recovered fungal filtrate, although glucose was being produced. A SSF with washing cycles was designed to recover the glucose, examining several parameters including nutrients added, length between washing cycle and washing solution used. The highest glucose was obtained from a daily washing cycle, with the use of 40.0 x 106 spores/g and the addition of YE (0.0175 g/g) and minerals to 80% (w/v) MC to the Sago hampas. This resulted in the conversion of 46.53 % of the available starch into glucose after six days of incubation. This was compared with the initial continuous SSF over 21 days of incubation which gave 10.11% conversion of starch.

The processes explored in this work could enable the creation of novel biorefining processes, using on-site produced cellulase enzymes to hydrolyse underutilised crops to a sugar-rich hydrolysate. This, as well as the sugar-rich filtrate produced with the Sago hampas, could then be used in the production of biofuels and/or biochemicals.

Item Type: Thesis (University of Nottingham only) (MPhil)
Supervisors: Chong, Mei Fong
Tucker, Gregory
Soh, Aik Chin
Du, Chenyu
Keywords: Biological pretreatment, vital resources, energy security, biofuel, biochemical, lignocellulosic
Subjects: T Technology > TP Chemical technology
Faculties/Schools: University of Nottingham, Malaysia > Faculty of Science and Engineering — Engineering > Department of Chemical and Environmental Engineering
Item ID: 41921
Date Deposited: 26 Sep 2017 09:36
Last Modified: 13 Oct 2017 01:11

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