Abstract
High residual oil content in antibiotic production waste mother liquor makes solid–liquid separation of fermentation residue and wastewater difficult. A yeast-based pretreatment process was established for the removal of oil and promotion of solid–liquid separation in antibiotic production wastewater treatment systems. Six yeast strains acquired from different sources were inoculated into sequencing batch reactors (SBR) in pilot and full-scale wastewater treatment plants. Oil removal rates were 85.0%–92.0% and 61.4%–74.2%, and sludge settling velocities (SV) were 16.6%–21.3% and 22.6%–32.0% for the pilot and full-scale operations, respectively. 18S rRNA gene clone libraries were established to track the fates of the inoculated yeasts, which showed that Candida tropicalis was dominant in the full-scale plant. The fungi and bacteria gene copy ratio determined by quantitative polymerase chain reaction was 14.87 during stable field operation, indicating that yeast successfully colonized. Both the pilot and full-scale studies proved that yeast can be used to promote solid–liquid separation, and yeast systems are a stable and effective method for oil-containing fermentation antibiotic production wastewater pretreatment.
Highlights
Antibiotic production methods consist of microorganism fermentation, as well as chemical and half-chemical synthesis
The fermentation antibiotic production waste mother liquor was characterized as acidic with high organic loading (SCOD > 20,000 mg/L)
Soybean oil was added as the fermentative medium for paromomycin production, with high-strength oil residue found in the production wastewater (13,800 ± 38 mg/L)
Summary
Antibiotic production methods consist of microorganism fermentation, as well as chemical and half-chemical synthesis. Most antibiotics in use, such as aminoglycosides, are produced by microbial fermentation. Production processes are roughly divided into fermentation, filtration, extraction, and refinement. The main pollutants are waste mother liquor and fermented residue. Waste mother liquor commonly contains substrates (e.g., oil, starch, cellulose, polysaccharides), target products (e.g., antibiotics), by-products (e.g., glyoxylate), and extraction solvents [1,2]. To produce aminoglycosides (such as paromomycin and ribostamycin), soybean oil is widely used in the fermentative substrate as a high-quality carbon source, oxygen vector, and antifoam compound
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