Document Type

Thesis - Open Access

Award Date

2015

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

William R. Gibbons

Keywords

canola meal, fungal processing, oilseeds, protein production

Abstract

The main limitation of meals from canola and other Brassica spp. is the presence of glucosinolates (GLS), which are anti-nutritional and can even be toxic at high ingestion levels. Furthermore, large amounts of GLS can reduce palatability for livestock and thus reduce intake and growth rates. For this reason canola was bred to contain lower levels of GLS (<30 >μmol/g) and erucic acid (< 2%). However, feed inclusion rates are still limited to ~30%, and this reduces the value of canola meal. The goal of this thesis was to optimize a pretreatment and fungal conversion process to enhance the nutritional value of canola meal. Various combinations of physical/chemical pretreatments, fungal cultures, and incubation methods were investigated to metabolize GLS into cell mass, CO2, or other non-toxic components. These treatments also served to hydrolyze canola meal fiber into carbohydrates which were then metabolized by the fungi into single cell protein. Solid-state incubation conditions were initially tested, since filamentous fungi are well adapted to grow at lower moisture levels, and this would potentially reduce contamination issues with bacteria. Flask trials were performed using 50% moisture, hexane extracted (HE) or cold pressed (CP) canola meal, with incubation for 168 h at 30ºC. On HE canola meal Trichoderma reesei (NRRL-3653) achieved the greatest increase in protein content (23%), while having the lowest residual levels of sugar (8% w/w) and GLS (0.4 μM/g). On CP canola meal T. reesei (NRRL-3653), Aureobasidium pullulans (NRRL-58522), and A. pullulans (NRRL-Y-2311-1) resulted in the greatest improvement in protein content (22.9, 16.9 and 15.4%, respectively), while reducing total GLS content from 60.6 μM/g to 1.0, 3.2 and 10.7 μM/g, respectively. GLS levels were reduced to 65.5 and 50.7% by thermal treatments while solid-state microbial conversion further reduced GLS up to 99 and 98% in HE and CP canola, respectively. Fiber levels increased due to the concentration effect of removing oligosaccharides and GLS. Submerged incubation conditions were also tested, as this approach is more commonly used in industry due to easier material handling and process control. Flask trials were performed using 10% moisture content HE or CP canola meal, with incubation for 168 h at 30ºC while being agitated at 150 rpm. Canola meals were either subjected directly to submerged incubation with the fungal strains, or were first saccharified with a cellulase enzyme cocktail and then incubated with the fungi. Aureobasidium pullulans (Y-2311-1), Fusarium venenatum and Trichoderma reesei resulted in the greatest improvements in protein levels in HE canola meal, at 21.0, 23.8, and 34.8%, respectively. These fungi reduced total GLS content to 2.7, 7.4, and 4.9 μM/g, respectively, while residual sugar levels ranged from 0.8-1.6% w/w. In trials with CP canola meal, the same three fungi increased protein levels by 24.6, 35.2, and 37.3%, and final GLS levels to 6.5, 4.0, and 4.7 μM/g, respectively, while residual sugar levels ranged from 0.3-1.0 % w/w. P. kudriavzevii was the only fungi able to significantly reduce ADF in both saccharified HE and CP canola meal, representing a reduction of 6.5 and 9.6%, respectively. Similar to solid-state incubation, most cases resulted in an increase of fiber levels due to the concentration effect of removing oligosaccharides and GLS.

Library of Congress Subject Headings

Canola--Biotechnology

Oilseed plants--Biotechnology

Canola meal

Description

Includes bibliographical references (pages 120-142)

Format

application/pdf

Number of Pages

157

Publisher

Soouth Dakota State University

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Rights Statement

In Copyright