Optimizing bio-physical conditions and pre-treatment options for breaking lignin barrier of maize stover feed using white rot fungi
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Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
Animal Nutrition
Abstract
The greatest limitation to utilization of maize stover by ruminants as a feed is the high concentration of
lignin, which limits fibre digestibility.However, ruminants can effectively utilize maize stover if its nutritive
value is improved using white rot fungal species. This study was designed to determine optimal biophysical
conditions for mycelial growth and select the most ideal fungal species and pre-treatment options
for improving nutritive value of maize stover. Four popular edible Pleurotus fungal species (viz.
Pleurotus florida, Pleurotus ostreatus, Pleurotus sajor caju and Pleurotus pulmonarius) were subjected to
varying temperatures, pH levels, hydrogen peroxide (H2O2) concentration and illumination to establish the
extent ofmycelial growth rate. Inclusion of H2O2was used to determine optimal levels for preservation and
prevention of contamination from other indigenous microbiota. Effects of pre-treatment options on
chemical composition and nutritive value of maize stover were also examined. Mycelial growth rate of
Pleurotus species on potato dextrose agar (PDA) varied (P < 0.05) with temperature, pH level and H2O2
concentration following a quadratic trend. Optimal temperature, pH and H2O2 concentration for mycelial
growth on PDA were 25 C, 5 and 0.01 mL/L, respectively. Under the different bio-physical conditions,
P. sajor caju had the highest mycelia density and growth rate. Chemical composition of solid-state fermented
maize stover differed (P < 0.05) among the Pleurotus species. Maize stover fermented with P. sajor
caju had the highest crude protein (CP) of 86.6 g/kg DM, in-vitro dry matter digestibility (IVDMD) of 731 g/
kg DM, in-vitro organic matter digestibility (IVOMD) of 670.4 g/kg DM and metabolizable energy (ME) of
10.0 MJ/kg DM but with the lowest lignin (sa) of 50 g/kg DM. At 25 C, P. sajor caju had the highestmycelial
growth rate on PDA and highest lignin (sa) breakdown in the maize stover substrate. It was, therefore,
selected as the most ideal fungal species for improving nutritive value of maize stover. Pre-treatment of
maize stover with Lactobacillus plantarum and molasses under anaerobic condition for 7 days before
inoculation with P. sajor caju resulted into a substratewith the highest (P < 0.05) CP (96.6 g/kg DM), IVDMD
(752.3 g/kg DM), IVOMD (687.2 g/kg DM) and ME (10.2 MJ/kg DM). However, neutral detergent fiber
exclusive of residual ash (NDFom) and lignin (sa) fractions decreased (P < 0.05) as a result of subjecting
maize stover to pre-treatment with L. plantarum and molasses prior to fermentation with P. sajor caju.
Description
Keywords
Crop residues, Lactobacillus plantarum, Lignin biodegradation, Mycelial growth
Citation
Atuhaire, A. M., Kabi, F., Okello, S., Mugerwa, S., & Ebong, C. (2016). Optimizing bio-physical conditions and pre-treatment options for breaking lignin barrier of maize stover feed using white rot fungi. Animal Nutrition, 2(4), 361-369. http://dx.doi.org/10.1016/j.aninu.2016.08.009