Isolation and identification of latex-degrading bacteria

Abstract

Latex-degrading bacteria have contrasting potential to offer sustainable waste biodegradation solutions while simultaneously threatening manufacturing productivity, product shelf-life, and overall quality. This study aimed to isolate, identify, and characterize latex-degrading bacteria to achieve a deeper understanding of their degradation abilities. Bacterial strains were isolated from raw latex and soil samples from the Bukit Kuantan Research Station of the Malaysia Rubber Board using latex-overlay agar and a three-quadrant streaking method to yield single colonies.  Identification was carried out using conventional biochemical methods, including Gram staining, catalase testing, and Indole, Methyl Red, Voges-Proskauer, and Indole, Methyl Red, Voges-Proskauer, and Citrate (IMViC) tests, alongside Sanger DNA sequencing.  To characterize degradation activity, liquid natural latex was incubated with the isolated bacteria for seven days at 37 °C.  The resulting molecular and physical changes were quantified using (Fourier transform infrared spectroscopy) FTIR spectroscopy, total solid content (TSC), and DRC analyses. A total of 10 distinct bacterial colonies exhibiting clearing zones on the latex overlay were selected for identification.  Morphological and biochemical screening determined that six isolates were Gram-negative and four were Gram-positive, while all 10 isolates uniformly tested catalase-positive and indole-negative.  Further identification of two out of ten bacterial isolates by Sanger sequencing identified as Lysinibacillus xylanilyticus and Stenotrophomonas geniculata.  FTIR analysis verified successful latex degradation, displaying extra minor peaks of C-C and C-O stretching compared to the untreated negative control.  Degradation was further validated by physical measurements, which resulted in reduced post-degradation TSC and DRC values of 20.64% and 16.61%, respectively. The study successfully isolated ten bacterial strains from raw latex and soil, and confirmed the specific latex-degrading capacities through comprehensive biochemical, molecular, and physical characterization.