Triticale grain fermentation for production of bio ethanol and animal feed

Du Toit, Lorinda (2019-04)

Thesis (Meng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: High quantity of starch and relative high protein content, compared to other cereal grains, make triticale ideal as a feedstock for production of bioethanol and animal feed. It is mostly planted as feed for livestock and ground cover, therefore (if planted on marginal lands) no competition exists with the human food industry, as is the case when maize or wheat is used for bioethanol production. The conventionally applied warm conversion process of starch to ethanol, requires high heat energy inputs, thus increasing the cost of production. The lesser used cold conversion process requires less heat energy, but a higher enzyme dosage is required to achieve similar conversion efficiencies and ethanol yields. Therefore, reduction in enzyme dosage in conjunction with lower energy requirements will decrease operation costs for the cold conversion process, possibly increasing profitability. The main aim of this study was to optimise four process configurations, using whole-milled and debranned-milled triticale grains as feedstock for the conventional warm and cold conversion processes, in an effort to reduce the enzyme dosage required to achieve industry standards for fermentation performance (above 90% of the theoretical maximum yield). The next step was to scale up all process configurations and determine which configuration yields the best quality distiller’s dried grains with solubles (in terms of protein and fibre content) while maintaining industry standards for fermentation performance. A central composite design (CCD), with enzyme dosage and hydrolysis time as independent variables, was used and experiments were carried out in 250 mL flasks. Fermentation performance was measured in terms of ethanol concentration, ethanol yield and ethanol productivity. Statistical models, relating independent variables and optimal performance measures, were developed. The models were validated in 5 L and 100 L scale-up experiments. The quality of distiller’s dried grains with solubles (DDGS) produced from the scaled-up experiments were measured an compared across all process configurations and to canola oil cake and soy protein. Of the 100 L scaled-up experiments, the warm debranned configuration performed best with a final ethanol yield (as a % of the theoretical maximum) of 94.2%. The cold debranned configuration and warm whole-milled configuration came second and third, with 92.1% and 90.3% respectively. The cold whole-milled configuration did not reach the benchmark of 90% yield. Productivities for warm whole-milled and debranned grains were 1.7 and 2.5 g/L/h respectively, while cold whole-milled and debranned configurations achieved 1.4 and 2.2 g/L/h. Debranning of grains had a significant (p<0.05) positive effect on both fermentation performance and quality of DDGS of the warm and cold processes. Moreover, DDGS produced from the cold debranned configuration had the highest quality. With a 44% crude protein and 13.85% acid detergent fibre content, it is ideal as a high-protein animal feed for monogastric animals.

AFRIKAANSE OPSOMMING: Met ‘n hoë hoeveelheid stysel en ‘n relatiewe hoë proteïeninhoud, in vergelyking met ander grane, is korog ideaal as voermateriaal vir die produksie van bioëtanol en diervoer. Dit word meestal geplant vir veevoer en grondbedekking, en is daarom (as dit op marginale lande geplant word) geen kompetisie vir die menslike kos industrie nie, soos die geval is wanneer mielies of koring gebruik word vir die produksie van bioëtanol. Die konvensioneel toegepaste warm-omskakelingsproses van stysel na etanol benodig hoë hitte-energie insette, en verhoog dus die koste van produksie. Die minder gebruikte koue-omskakelingsproses vereis minder hitte, maar ʼn hoër ensiem dosis om soortgelyke omskakelingsdoeltreffendheid en etanolopbrengste te bereik. Daarom sal vermindering in ensiem dosis saam met laer energie vereistes operasionele kostes vir die koue-omskakelingsproses verminder, en moontlik winsgewendheid verhoog. Die hoofdoel van hierdie studie was om vier proseskonfigurasies te optimeer deur gebruik te maak van heel-gemaalde en ontsemelde-gemaalde koroggraan as voermateriaal vir die konvensionele warm en nuwer koue omskakelingsprosesse, om die nodige ensiem dosering te verminder maar steeds bedryfstandaarde vir fermentasie prestasie te behaal (bo 90% van die teoretiese maksimum opbrengs). Die volgende stap was om alle proseskonfigurasies op te skaleer en te bepaal watter opset die beste gehalte distilleerders droë korrels lewer (in terme van proteïen- en veselinhoud), terwyl industriële standaarde vir fermentasie prestasie behou word. 'N sentrale saamgestelde ontwerp (SSO), met ensiem dosering en hidrolise tyd as onafhanklike veranderlikes, is gebruik en eksperimente is uitgevoer in 250 ml flesse. Fermentasie prestasie is gemeet in terme van etanol konsentrasie, etanol opbrengs en etanol produktiwiteit. Statistiese modelle, met betrekking tot onafhanklike veranderlikes en optimale prestasiemaatreëls, is ontwikkel. Die modelle is gevalideer in 5 L en 100 L opgeskaleerde eksperimente. Die gehalte van distilleerders droë korrels en oplosbares (DDKO), wat uit die opgeskaleerde eksperimente geproduseer is, is gemeet en vergelyk tussen proseskonfigurasies en met kanola oliekoek en soja-proteïen. Van die 100 L eksperimente het die warm ontsemelde konfigurasie die beste werkverrigting gehad met ʼn finale etanol opbrengs (as ʼn persentasie van die teoretiese maksimum) van 94.2%. Die koue ontsemelde en warm heel-gemaalde konfigurasies het tweede en derde gekom, met 92.1% en 90.3% onderskeidelik. Die koue heel-gemaalde konfigurasie het nie die doel van 90% opbrengs behaal nie. Produktiwiteit vir warm heel-gemaalde en ontsemelde graan was 1.7 g/L/h en 2.5 g/L/h onderskeidelik, terwyl koue gemaalde en ontsemelde konfigurasies 1.4 g/L/h en 2.2 g/L/h bereik het. Ontsemeling van korog het 'n beduidende (p <0.05) positiewe effek op beide fermentasieprestasie en gehalte van DDKO van die warm en koue prosesse gehad. Verder het DDKO geproduseer uit die koue ontsemelde konfigurasie die hoogste gehalte gehad . Met 'n ru-proteïen konsentrasie van 44% en 13.85% suurvasmiddel-veselinhoud, is dit ideaal as 'n hoë-proteïen voer vir monogastriese diere.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106091
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