Studies on biodegradation of synthetic detergents by microorganisms

Abstract

Most houses in Japan were provided with cesspool- or septic tank-percolation field system for domestic sewage disposal. The author carried out a two-year test on biodegradation of linear aklylate sulfonate (LAS) under the cesspool-percolation field, prior to the detergent conversion to biodegradable surfactants. Good drainage was sustained with the test LAS cesspool in comparison with the former ABS cesspool; so the test cesspool-percolation field system maintained an unsaturated soil condition.Under aerobic and anaerobic conditions, analysis on bacterial flora of the LAS cesspool was carried out on soil and waste taken from the cesspool. Among LAS assimilable bacterial species as Micrococcus, Aerobacter, Flavobacter, Paracolobactrum, Alcaligenes and Pseudomonas, a Pseudomonas sp. appeared to play the main role in the process of surfactant biodegradation. The Pseudomonas was named as Pseudomonas surfactassimilas nov. sp..Taxonomical characteristics of Pseudomonas surfactassimilas nov. sp. are as follows;The strain is Gram-negative rods and motile with a polar flagellum. Branching is not found.Rods: 0.4 to 0.6 by 1.2 to 1.5 microns.Nutrient agar colonies: Circular, smooth, entire, flat, yellowish gray.Nutrient agar slant: smooth, glistening, transluent, yellowish gray, medium unchanged.Potato: Growth moderate, creamy to yellowish gray.Litmus milk: Unchanged.Aerobic, facultative.Non fluorescence on King's media.Catalase: Negative.Kovacs' oxidase test: Positive.Gelatin Stab: No liquefaction.Nitrates: Not reduced.Acetylmethyl carbinol: Not produced.Urease: Negative.Indol: Not produced.Hydrogen sulfide: Not produced.Ammonium citrate: Not utilized.Starch: Not hydrolyzed.Casein: Not hydrolyzed.Cellulose: Not attacked.Glucose, lactose, sucrose: Not fermented.Citric acid, tartaric acid, succinic acid, acetic acid, fumaric acid: Used as a sole source of carbon.Valeric acid, propionic acid, butyric acid: Not utilized as a sole source of carbon, but used under existence of vitamins.Phenol (1%): Growth observed after twice inoculation on synthetic broth as a sole source of carbon.Surfactants with straight alkyl chain: Utilized as a sole source of carbon.Temperature relations: 20-37°C, optimum 30°C.Optimum pH: 7.0Source: Isolated from soil and waste of cesspool.When waste water was treated under aerobic circumstances, surfactants with straight alkyl chain could be decomposed by biological oxidation to the extent comparable with, or more than, the degradation of general organic substances. The cesspool-percolation field system easily maintained an unsaturated condition to avoid excessive ponding in the percolation field by periodic supply of waste water which provided aerobic condition.