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From NCERT Chemistry: Textbook for class XII, Part II [1, p. 461]:

Main problem that appears in the use of detergents is that if their hydrocarbon chain is highly branched, then bacteria cannot degrade this easily. Slow degradation of detergents leads to their accumulation. Effluents containing such detergents reach the rivers, ponds, etc. These persist in water even after sewage treatment and cause foaming in rivers, ponds and streams and their water gets polluted.

These days the branching of the hydrocarbon chain is controlled and kept to the minimum. Unbranched chains can be biodegraded more easily and hence pollution is prevented.

Why are straight chain detergents generally biodegradable while branched chain detergents are non biodegradable? Basically, how does branching affect biodegradation?

Is there any more detail/ better explanation than this or explanation from any other view point?

References

  1. NCERT. Chemistry: Textbook for Class XII. Part II, Reprint: August 2019 Bhadrapada 1941; M. Siraj Anwar, Shveta Uppal, Arun Chitkara, Bibash Kumar Das, R.N. Bhardwaj, Mukesh Gaur, Series Eds.; National Council of Educational Research and Training: New Delhi, 2007. ISBN 978-81-7450-716-7. (PDF)
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According to Scott and Jones1:

... problems arise with branched alkyl chains, a side chain methyl group or a gem-dimethyl-branched chain cannot undergo β-oxidation by microorganisms and must be degraded by loss of one carbon atom at a time (α-oxidation).

* text by the authors, highlighting and hyperlinking by me.

A study by Whyte et al2 on the degradation of alkanes by Rhodococcus yielded similar findings:

After 28 days of growth at 5°C in MSM containing 0.1% diesel fuel, Rhodococcus sp. strain Q15 degraded almost all the n-alkanes (C10 to C21) and, to a lesser degree, many of the branched alkanes found in diesel fuel.

P.s: both of these articles are open access, and explain the biodegradation process quite well. You can refer to them directly if you need more detail or specific examples.

References:

  1. Scott, Matthew J., and Malcolm N. Jones. “The Biodegradation of Surfactants in the Environment.” Biochimica et Biophysica Acta (BBA) - Biomembranes, vol. 1508, no. 1–2, 2000, pp. 235–51. doi:10.1016/S0304-4157(00)00013-7.
  2. Whyte, L. G., et al. “Biodegradation of Variable-Chain-Length Alkanes at Low Temperatures by a Psychrotrophic Rhodococcus Sp.” Applied and Environmental Microbiology, vol. 64, no. 7, 1998, pp. 2578–84. PMID: 9647833
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