Branched hexatriacontane

Biodegradation in soil

Administrative data

Endpoint:

biodegradation in soil

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

Not available

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Published literature data.

Data source

Reference

Reference Type:

publication

Title:

Further Research into the Aerobic degradation of n-Alkanes in a Heavy Oil by a pure culture of A Pseudomonas SP.

Author:

Setti L., Lanzarini G., Pifferi P. G., and Spagna G.

Year:

1993

Bibliographic source:

Chemosphere, Vol 26 No. 6, pp 1151 - 1157, 1993

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Please see details on method in the section 'Any other information on material and methods'.

GLP compliance:

not specified

Test type:

laboratory

Test material

Test material information

Constituent 1

Reference substance name:

n-alkanes C13 - C35

IUPAC Name:

n-alkanes C13 - C35

Details on test material:

All chemicals used were reagent grade and purchased froim Carlo Erba (Milan). Heavy oil (a residue of an industrial treatment in which the inorganic sulfur was removed_ was obtained from AGIP-Petroli (Rome)

Radiolabelling:

not specified

Study design

Oxygen conditions:

aerobic

Soil classification:

not specified

Duration of test (contact time)

Duration of test (contact time) 1

Duration:

15 d

Duration of test (contact time) 2

Duration:

30 d

Results and discussion

% Degradation

% Degradation 1

% Degr.:

>= 50 - <= 100

Parameter:

other: C13 degradation

Sampling time:

15 d

% Degradation 2

% Degr.:

100

Parameter:

other: C13 degradation

Sampling time:

31 d

% Degradation 3

% Degr.:

0

Parameter:

other: C24 degradation

Sampling time:

15 d

% Degradation 4

% Degr.:

67 - 84.7

Parameter:

other: C24 degradation

Sampling time:

31 d

% Degradation 5

% Degr.:

>= 40 - <= 65.1

Parameter:

other: C35 degradation

Sampling time:

31 d

Transformation products:

not specified

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

Any other information on results incl. tables

The degradation of n-alkanes follows a well-known sequence characterised by the fact that dropping decreases as the molecular weight of the aliphatic compounds increases (Table 1). After one month of fermentation, degradation is over 60% for all n-alkanes, whereas after 15 days only C13 and C14 are degraded over 50%.

Gas chromatographic analyses clearly highlight this phenomenon (please see Fig. 2 attached) and they show that the iso-alkanes, phytane and pristane, are more resistant to degradation.

The degradation of the n-alkanes (Table 1) leads to a heavy oil residue richer in high molecular weight n-alkanes (please see Fig 3 attached). The percentage of n-alkanes above C28 increases between the 15th and 31st day of fermentation, as consequence of degradation of the n-alkane from C13 to C28. The percentage of n-alkanes from C17 to C28 reached its peak at 15 days.

Another finding emerges from examining n-alkane degradation as a function of the incerse of hydrocarbon chain lenght (please see Fig 4 attached). All fermentation trials exhibited the same degradation pattern. After 15 days, two difference linear behaviour patterns were observed one for n-alkanes from C13 to C16 and another for those over C17. By extrapolating the two lines, a changing degradation point (α) is obtained; it corresponds to an average value, n of 16.0 +/-0.6.

After 31 days the value of (α) is still constant, whereas the soilid n-alkane group breaks down into two sub-groups with a changing degradation point (β), whose average value, n, is 27.0 +/-1.0. These two sub-groups include the low solid alkanes, C17 -C28 and the high ones above C28. The first sub-group shows a constant degradation pattern for entire range of compounds while, in the second, degradation depends on the hydrocarbon chain length.

Table 1 n-Alkane degradation percentages in five different trials at two fermentation times

Carbon number (n)	15 days			31 days
	I	II	III	IV	V
13	50	76	100	100	100
14	22.4	43.8	70.1	82.1	100
15	8.8	21.5	36.3	71.4	93.8
16	5.0	9.1	20.0	64.4	86.4
17	0	3.9	10.7	64.3	86.1
18	-	1.4	8.0	66.8	86.4
19	-	0	8.2	63.6	86.1
20	-	-	6.2	62.5	85.4
21	-	-	5.6	66.3	85.6
22	-	-	6.9	67.6	84.7
23	-	-	6.4	66.7	85.5
24	-	-	0	67.0	85.0
25	-	-	-	65.8	84.3
26	-	-	-	66.1	84.7
27	-	-	-	63.3	83.6
28	-	-	-	67.2	69.2
29	-	-	-	65.1	70.0
30	-	-	-	64.0	78.4
31	-	-	-	55.9	73.8
32	-	-	-	58.6	70.0
33	-	-	-	56.5	72.0
34	-	-	-	47.4	70.5
35	-	-	-	40.0	65.1

Applicant's summary and conclusion

Conclusions:

Setti et al (1993) measured the concentration of n-alkanes up to C35 in a heavy oil, using a Pseudomonas culture. Degradation was faster for lower C number, and three distinct groups were identified. Around C34 the extent of degradation was approx. 65% at 31 days.

Executive summary:

The microbal degradation of the saturated fraction of a heavy oil was examined in aerobic conditions employing a pure culture of a Pseudomonas sp. isolated from soil. A new model of n-alkane degradation is proposed. The n-alkanes were divided into three degradation groups i) liquid n-alkanes, C12 -16; 11) low solid n-alkanes C17 -28; iii) high solid n-alkanes, above C28. Our results show that n-alkane degradation depends on chemical and physical factors such as solubility and surface tension