Provision and Identification of Local Microorganisms Based on Lake Toba Water and Its Utilization on Plastic Biodegradation

Abstract

Local Microorganisms (LMO) are fermentation solutions made from agricultural, plantation and household organic
waste. LMO is made by mixing three main sources of ingredients, namely a glucose source, a complex carbohydrate
source, and a microorganism source which are next fermented anaerobically. The LMO solution made can be used
to reduce plastic pollution through biodegradation. This research aims to analyse the variation of the volume of Lake
Toba water as a source of microorganisms in making LMO which is used to degrade plastic and to identify plastic
degrading local microorganisms. The research methodology consisted of making standard curves and growth curves,
making LMO, testing the biodegradation of Low-Density Polyethylene (LDPE) plastic, isolating microorganisms,
performing biochemical test, testing the clear zone for plastic degrading microorganisms, and identifying
microorganisms. LMO was made by mixing raw materials according to the ratio of microorganism volume to
substrate namely 20:80 (% v/v); 30:70 (% v/v); and 40:60 (% v/v) which were fermented for 99 hours at temperature
of 37 C. The results show that there is a change in LMO pH before and after fermentation namely from 4.75; 4.9;
and 4.94. to 3.46; 3.45; and 3.48. The decrease in pH occurs due to the activity of microorganisms that produced
organic acids. The three variations of LMO produce degradation percentage of LDPE plastic, namely 2.353% w/w;
3.012% w/w; and 4.023% w/w. The variation ratio of 40:60 (% v/v) shows the largest percentage of LDPE
degradation, which was then isolated, and 5 isolates were obtained. The five isolates were also screened to validate
their potential in degrading LDPE and 2 isolates were found which produced clear zones which were identified by
gram staining as Staphylococcus aureus and Streptococcus sp.