Community succession and decomposition of microbial biomass during the composting of pot ale liquor explores the innovative use of composting to treat liquid distillery waste. The study emphasizes the efficiency of microbial communities in degrading dead yeast cells found in pot ale, achieving a remarkable reduction in Biological Oxygen Demand (BOD). It examines the microbial succession and community dynamics during the composting process, highlighting the importance of maintaining a stable thermophilic community. This research is valuable for environmental scientists and waste management professionals seeking sustainable waste treatment solutions.

Key Points

  • Explores microbial community dynamics during pot ale liquor composting.
  • Achieves a 99% reduction in Biological Oxygen Demand (BOD) through microbial degradation.
  • Examines the role of temperature in microbial succession during composting.
  • Utilizes innovative methods like PLFA and CLPP for microbial community analysis.
newtopiccyclegrowin
8 pages
Microbiology
newtopiccyclegrowin
8 pages
Microbiology
255
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Microbial Processes during Composting
Microbial Biosystems: New Frontiers
Proceedings of the 8
th
International Symposium on Microbial Ecology
Bell CR, Brylinsky M, Johnson-Green P (eds)
Atlantic Canada Society for Microbial Ecology, Halifax, Canada, 1999.
Community succession and decomposition of microbial biomass
during the composting of pot ale liquor
Campbell, C.D.
1
and Cooper, J.N.
1, 2
1
Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, UK, AB15 8QH and
2
Highland Malt Distilling Ltd, Kirkwall, Orkney,UK
ABSTRACT
Composting is normally viewed as a solid waste treatment process. In a new approach we
have used composting to treat a liquid distillery waste, pot ale, comprised of predominantly
dead yeast cells. The process is operated in continuous, batch-fed mode and degradation
efficiency is dependent on maintaining a stable microbial community. The degradation of
dead microbial biomass in the pot ale liquor was highly efficient resulting in a reduction of
the five day Biological Oxygen Demand (BOD
5
) by 99%. The composting of tree bark and
pot ale liquor was studied in microcosms to determine the succession of microbial
communities during the self-heating phase. Microbial community analyses (biomarkers
and sole-carbon source tests) were used to characterize the successional changes which
correlated with both physical and chemical changes in the substrate.
Introduction
Conventionally, composting is viewed as a low technology method to convert and stabilize
low value organic wastes into a substrate useful for growing plants or mushrooms.
However, the need for new sustainable waste treatment processes means composting is
being considered for the bioremediation of contaminated solid wastes [15] and soil [1] as
well as biologically active filters for remediating polluted waste waters [20] and
contaminated air [17]. In addition, traditional agricultural and horticultural composts are
being recognized increasingly for their biological quality, e.g. by the presence of growth
promoting organisms [21] and organisms antagonistic to plant pathogens [13]. New
applications and a new appreciation of the value of the composting process require greater
understanding of which factors regulate microbial diversity during composting.
Microbial succession during composting is a classic ecological example of how the
growth and activity of one group of organisms creates the conditions necessary for the
growth of others. Temperature is the main driving force of succession but it also interacts
with other environmental regulators such as pH, redox potential and gaseous exchange as
well as the availability of C and energy sources. The turnover of biomass is an essential
feature of community succession and total biomass is often seen to decline with time after
the initial rapid growth [11,14]. Direct evidence of organisms living off necromass is
difficult to obtain, although yeasts, usually reported as zymogenous organisms, have been
reported living inside the disrupted cleistothecia of thermophilic fungi [5].
Our view of succession during composting is largely based on conventional plating and
isolation procedures. More recently molecular biology techniques [16], phospholipid fatty
acid analysis (PLFA) [12], and community level physiological profiles (CLPPs) using sole
Microbial Processes during Composting
C source tests (Biolog) [14] have been used. The aim of this paper is to discuss the utility
of some current methods of microbial community analysis for investigating the ecology of
composting. A novel composting process used to treat pot ale liquor, a waste byproduct of
the manufacture of whisky was studied. The efficiency of this process depends on
maintaining a stable thermophilic community. The process called TAPP (Thermogenic,
aerobic, plug-flow, percolation; UK Patent Application No GB 2322623A) was devised to
treat pot ale liquor by percolating the liquor through compost stacks made from bark and
wood wafers. Pot ale liquor cannot be discharged directly to waters because of its high
biological oxygen demand (BOD), low pH and high Cu content. The solids content of pot
ale comprise dead yeast cells and the efficiency of the process depends on developing a
microbial population capable of degrading this necromass. The process produces a leachate
with a BOD
5
reduced from 20000 to <100 ppm; the pH increased from 3.0 to between 5.0
and 6.5 and a Cu content reduced from 10 ppm to 16 ppb. The Cu is adsorped mainly to
polyphenolic compounds in the bark but it was noted in early trials that bark on its own did
not reduce the BOD as well as a combination of bark and wood wafers. Consequently, the
microbial communities on the two different woody substrates, bark and wood wafers, were
examined to test the hypothesis that they supported different microbial communities.
Materials and Methods
Experimental design
Pulverized fresh conifer bark and wood wafers were weighed separately into 1.5 L Kilner
jars after being amended with either pot ale liquor or water (10% by volume). Thereafter
pot ale liquor or water was added (2% v/v) every two days. The jars were closed with
cotton wool bungs to allow free gas exchange and incubated at a predetermined
temperature program starting at 30°C for one day and increasing by 10°C d
-1
up to 50°C
where it was maintained for a further 12 days. Samples were taken at 0, 7 and 14 d to
compare the temporal development of the microbial communities.
Microbiological analysis
Total viable counts (TVC) were made on fresh samples extracted and diluted using de-
ionized water and by spread plating onto Tryptone Soy Agar (TSA, 0.1 strength) and also
malt extract agar (MEA). Duplicate sets of plates were incubated at 25 and 50 °C and
counts made after 7 d. PLFA analysis was carried out on 10 g of freeze-dried sample using
the Bligh & Dyer [3] method to extract and purify lipids that were analyzed by GC using a
polar capillary column [8]. CLPPs were determined by direct incubation of compost
extracts in microtitre plates containing different C sources in individual wells to determine
changes in relative and absolute rates of utilization of individual substrates [4,10]. We
tested 125 C sources using BIOLOG GN plates and customized BIOLOG MT plates in
which the wells contained 30 additional, ecologically relevant C sources [4]. The 10
-2
dilution was used to inoculate the Biolog plates and duplicate sets of C source profiles were
inoculated and incubated at either 25 or 50°C to determine the profile of mesophilic and
thermophilic organisms respectively. Plates were read twice daily for 5 d and ANOVA of
the average well colour development over time was used to select comparable time points
to avoid confounding effects of inoculum density differences between treatments [9].
Respiration (CO
2
evolution) was measured on samples of 10 g in 100 cm
3
soil jars, by
Microbial processes during composting
measuring headspace CO
2
accumulated over 6 h, at 25°C and 50
o
C, using a gas
chromatograph.
Statistical analysis
Both the PLFA and CLPP multivariate data sets were analyzed by canonical variate analysis
(CVA), after first reducing the dimensionality of the variates to less than the number of
samples by principal components analysis (PCA). The mean Mahalanbois distance between
treatment groups was compared to simulated data to calculate significant effects [4]. The
CLPP data was also transformed by dividing by the AWCD before analysis. Treatment
means and least significant differences at 5% (LSD
0.05
) were calculated using a two way
(treatment x sampling date) ANOVA. All computations were performed using Genstat 5.3
(NAG Ltd., Oxford, UK).
Results
The wood wafers had a higher initial starting C:N ratio than the bark and also a higher pH
that was maintained over the 14 d (Table 1). The moisture content increased significantly
over the 14 d until it reached an equilibrium level of 70%. The addition of pot ale with a
C:N ratio of 4.8 significantly increased the N content of both bark and wood wafers but
more so in the bark (Table 1).
Table 1. Changes in moisture content (%mc), pH , %C and %N, total PLFA and
respiration in bark and wood wafers amended with pot ale liquor and incubated at 50°C .
Day % mc pH %C %N PLFA
tot
ηmol/g
Respiration
µg CO
2
-C/g/h
25°C50°C
Bark 0
7
14
62.6
64.3
71.2
4.1
4.2
4.2
43.7
47.5
47.3
0.42
0.39
0.36
81
89
83
18.8
9.9
5.2
50.2
31.3
17.2
Bark + pot ale 0
7
14
63.2
65.2
72.9
4.5
4.7
4.9
47.3
46.8
46.3
0.71
0.70
0.68
98
145
150
64.5
32.2
15.5
148.6
79.2
43.9
Wood wafers 0
7
14
59.3
55.0
68.4
7.2
6.6
6.7
53.2
52.6
52.6
0.19
0.20
0.19
74
66
49
12.3
8.0
4.4
49.7
32.2
14.9
Wood wafers + pot
ale
0
7
14
60.3
59.8
67.2
7.1
7.1
6.9
52.9
52.7
51.7
0.39
0.44
0.36
82
183
105
48.5
21.8
9.3
151.7
62.3
26.9
LSD
0.05
1.48 0.05 2.09 0.04 23 4.3 5.1
Respiration and biomass
Respiration (CO
2
-C evolution) rates were increased almost 3 fold after the addition of the
initial 10% of pot ale liquor and declined thereafter over the 14 d (Table 1). Respiration
was significantly higher in the bark with pot ale than in the wood with pot ale and was
approximately 2-4 times faster at 50
o
C than at 25
o
C. Biomass (PLFA
tot
) was stable (in
bark) or declined (in wood) without pot ale addition and was increased by 50% in the bark
/ 8
End of Document
255

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FAQs

What is the significance of microbial succession in composting?
Microbial succession is crucial in composting as it determines how different groups of microorganisms interact and thrive in the compost environment. Initially, thermophilic bacteria dominate due to high temperatures, which help decompose organic matter rapidly. As the temperature decreases, mesophilic organisms take over, further breaking down materials. This succession creates conditions favorable for the growth of various microbes, enhancing the overall efficiency of the composting process.
How does pot ale liquor affect microbial communities during composting?
Pot ale liquor, a byproduct of whisky production, contains high levels of dead yeast cells, which serve as a nutrient source for microbial communities during composting. The addition of pot ale significantly boosts the nitrogen content in compost, promoting microbial growth and activity. This study found that pot ale enhances the diversity and biomass of microbial populations, leading to more effective degradation of organic material and improved compost quality.
What methods are used to analyze microbial communities in composting?
The study employs several advanced techniques to analyze microbial communities, including Phospholipid Fatty Acid (PLFA) analysis and Community-Level Physiological Profiles (CLPP). PLFA analysis helps identify and quantify different microbial groups based on their lipid profiles, providing insights into community structure. CLPP assesses the metabolic capabilities of microbial communities by measuring their ability to utilize various carbon sources, revealing functional diversity and activity levels.
What are the environmental benefits of composting pot ale liquor?
Composting pot ale liquor offers significant environmental benefits by converting a waste product into a valuable resource. The process reduces the high Biological Oxygen Demand (BOD) of pot ale, making it less harmful to aquatic ecosystems if released. Additionally, composting helps stabilize organic waste, reduces landfill use, and produces nutrient-rich compost that can enhance soil health and promote sustainable agriculture.
What challenges are associated with composting pot ale liquor?
Challenges in composting pot ale liquor include managing the high acidity and copper content typical of distillery waste. These factors can inhibit microbial activity and affect compost quality. The study highlights the need for careful monitoring of pH levels and copper concentrations to ensure a stable microbial community and effective degradation of organic matter. Addressing these challenges is essential for optimizing the composting process and achieving desired environmental outcomes.

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