Development of integrated processes for the coproduction of inulin, protein, and ethanol from Jerusalem artichoke tubers in a biorefinery
| dc.contributor.advisor | Gorgens, Johann F. | en_ZA |
| dc.contributor.advisor | Chimphango, Annie F. A. | en_ZA |
| dc.contributor.advisor | Van Rensburg, Eugene | en_ZA |
| dc.contributor.author | Maumela, Pfariso | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. | en_ZA |
| dc.date.accessioned | 2021-03-08T11:26:46Z | |
| dc.date.accessioned | 2021-04-21T14:41:33Z | |
| dc.date.available | 2021-03-08T11:26:46Z | |
| dc.date.available | 2021-04-21T14:41:33Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Biorefining is an attractive approach to simultaneously address food supply, energy security and global warming. Furthermore, biorefining offers a sustainable strategy to utilise biomass, for energy production, thereby, reducing overreliance on fossil resources. The principal aim of the study was to evaluate the feasibility of a Jerusalem artichoke (JA) tuber-based biorefinery by integrating protein extraction to the conventional inulin extraction process, and subsequently hydrolysing the tuber residues with an enzyme cocktail of crude inulinases and commercial Cellic® CTec3 and Pectinex, for ethanol fermentation. The tuber mash was pressed for protein extraction from the juice and water extraction from the solid residues. Sequential water-extraction was used for protein and inulin, in the first and second step, respectively. The resulting tuber residues from the sequential extraction was hydrolysed and fermented into ethanol. Fed-batch culture was used to optimise the bioprocess conditions for recombinant endoinulinases production by Aspergillus niger. Comparison of sequential extraction sequences demonstrated that protein extraction in the first and second step, respectively, maximised the selectivity of the extraction and product yields. Both extraction steps utilised water as a solvent, and were optimised with respect to pH, solids loading and temperature for the selective extraction from each dedicated step from tubers. The soluble protein fraction contained a cumulative 71.8% of the protein present in tubers, while 17.1% was present in the inulin extracted in the subsequent step. The inulin yield was 67.6% of the inulin in the tubers, while 11.8% was co-extracted with the protein product. The protein extract was augmented by protein present in the press juice, obtained from tubers prior to the water extraction steps. High cell density fermentation of Aspergillus niger for recombinant endoinulinase production, was achieved through an exponential fed batch method. Endoinulinase production was growth associated at higher growth rates, achieving the highest volumetric activity (670 U/ml) and biomass concentration (33 g/L) at a growth rate (μ) of 0.07 h-1. Moreover, the significant decrease in enzyme activity (506 U/ml) and biomass substrate yield (0.043 gbiomassDW/gglucose) at low μ (0.04 h-1) was due to the high maintenance energy requirement. High biomass concentrations resulted in broth viscosity, which necessitated increased agitation for mixing and oxygen transfer. However, this led to pellet disruption and biomass growth in mycelial. Moreover, enzyme production profiles, product (Yp/s) and biomass (Yx/s) yield coefficients were not affected. High gravity simultaneous saccharification and fermentation (SSF) of the extraction residues, enriched in cellulose and inulin, was achieved with an optimised cocktail of enzymes. A combined inulin and cellulose conversion yield of 74% was achieved during fermentation at 21% w/v solids loading. The optimised enzyme cocktail improved the saccharification and fermentation of the residues, with an ethanol concentration and yield of 38 g/L and 83%, respectively, compared to an unoptimized cocktail with the same protein dosage, with 32 g/L and 59%, respectively, both at the maximum attainable solids loading of 21% w/v. Therefore, the current data demonstrated the potential of integrating a protein extraction with conventional inulin extraction from JA tubers and fermenting the residues into ethanol with an optimised enzyme cocktail. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Bioraffinering is ’n aantreklike benadering om gelyktydig voedselverskaffing, energiesekuriteit en aardverwarming aan te spreek. Verder bied bioraffinering ’n volhoubare strategie om biomassa te gebruik, wat aanhorigheid op fossielhulpbronne verminder. Die hoofdoel van die studie was om die uitvoerbaarheid van ’n aardartisjok (JA) -knolgebaseerde bioraffinadery te evalueer deur proteïenekstraksie saam met die konvensionele inulienekstraksieproses te integreer, en vervolgens die knolresidu’s met ’n ensiemmengsel van ru-inulienase en kommersiële Cellic® CTec3 en Pectinex te hidroliseer, vir etanolfermentasie. Die knolmengsel is gepers vir proteïenekstraksie vanuit die sap-en-waterekstraksie vanuit die soliede residu’s. Sekwensiële waterekstraksie is gebruik vir proteïen en inulien, in die eerste en tweede stap onderskeidelik. Die resulterende knolresidu’s vanuit die sekwensiële ekstraksie is gehidroliseer en gefermenteer na etanol. Gevoerde-lotkultuur is gebruik om die bioproseskondisies vir rekombinante endo-inulienaseproduksie deur Aspergillus niger te optimeer. Vergelyking van sekwensiële ekstraksiereekse het gedemonstreer dat proteïenekstraksie in die eerste en tweede stap, onderskeidelik, die selektiwiteit van die ekstraksie- en produkopbrengste gemaksimeer het. Beide ekstraksiestappe het water as oplosmiddel gebruik, en is geoptimeer met betrekking tot pH, vastestoflading en temperatuur vir die selektiewe ekstraksie vanuit elke toegewyde stap van knolle. Die oplosbare proteïenfraksie het ’n kumulatiewe 71.8% van die proteïen teenwoordig in knolle, bevat, terwyl 17.1% teenwoordig was in die inulien wat geëkstraheer is in die opvolgende stap. Die inulienopbrengs was 67.6% van die inulien in die knolle, terwyl 11.8% geëkstraheer is saam met die proteïenproduk teenwoordig in die perssap, verkry uit knolle voor die waterekstraksiestappe. Hoë seldigtheid van Aspergillus niger vir rekombinante endo-inulienaseproduksie is bereik deur ’n eksponensiële voerlotmetode. Endo-inulienaseproduksie is groei geassosieer by hoër groeitempo’s, wat die hoogste volumetriese aktiwiteit (670 U/ml) en biomassakonsentrasie (33 U/ml) by ’n groeitempo (μ) van 0.07 h-1, bereik het. Verder het die hoë onderhoudenergievereiste ’n beduidende afname in ensiemaktiwiteit (506 U/ml) en biomassa-substraatopbrengs (0.043 gbiomassaDW/gglukose) by lae μ (0.04 h-1) tot gevolg gehad. Hoë biomassakonsentrasies het sopviskositeit tot gevolg gehad, wat verhoogde roering vir vermenging en suurstofoordrag genoodsaak het. Hierdie het wel tot korrelversteuring en biomassagroei in miseliaal gelei. Ensiemproduksieprofiele, produk- (Yp/s) en biomassa- (Yx/s) opbrengskoëffisiënte is verder nie geaffekteer nie. Hoë gravitasie, gelyktydige sakkarifikasie en fermentasie (SSF) van die ekstraksieresidu’s, verryk in sellulose en inulien, is bereik met ’n geoptimeerde mengsel van ensiemes. ’n Kombinasie van inulien en sellulose omsettingsopbrengs van 74% is bereik deur fermentasie by 21% w/v vastestoflading. Die geoptimaliseerde ensiemmengsel het die sakkarifikasie en fermentasie van die residu’s verbeter, met ’n etanolkonsentrasie en -opbrengs van 38 g/L en 83%, onderskeidelik, in vergelyking met ’n mengsel wat nie geoptimeer is nie met dieselfde proteïendosis, beide by die maksimum vastestoflading van verkrygbare vastestoflading van 21% w/v. Daarom het die huidige data die potensiaal gedemonstreer van integrering van ’n proteïenekstraksie met konvensionele inulienekstraksie uit JA-knolle en fermentering van die residu’s na etanol met ’n geoptimeerde ensiemmengsel. | af_ZA |
| dc.description.sponsorship | The financial assistance of the Centre for Renewable and Sustainable Energy Studies (CRSES) and National Research Foundation (NRF) towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not necessarily to be attributed to the CRSES and NRF. | en_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | xvii, 152 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110124 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Jerusalem artichoke -- Biotechnology | en_ZA |
| dc.subject | Biorefinary | en_ZA |
| dc.subject | Inulin | en_ZA |
| dc.subject | Ethanol | en_ZA |
| dc.subject | Protein | en_ZA |
| dc.subject | Fermentation products industry | en_ZA |
| dc.subject | UCTD | |
| dc.title | Development of integrated processes for the coproduction of inulin, protein, and ethanol from Jerusalem artichoke tubers in a biorefinery | en_ZA |
| dc.type | Thesis | en_ZA |