The depletion of fossil fuel reserves requires advance anticipation through the search for alternative energy from renewable natural resources. Microalgae have been known as potential organisms for biodiesel feedstock. However, in order to be developed on a large scale, microalgae must have superior traits so that further development becomes more comfortable and cheaper. Tropical lakes are a source of superior microalgae adapted to moderate conditions which can later save operational costs in large-scale production. Situ Gintung and Situ Pamulang are the two largest lakes in South Tangerang, Indonesia and are potential sources of microalgae. Four microalgae isolates from both lakes have been identified, and their potential has been examined. Within an observation period of 18 days, they showed similar growth patterns reaching more than 108 cells mL−1 on day 14 and were able to resist increasing pH. The microalgae were identified through morphological observations and the sequencing of 23S rRNA genes with phylogenetic analysis. Each strain has a positive quality. Isolate G4-3, which was identified as Micractinium conductrix, and P5-4, which was identified as Monoraphidium sp., yielded biomass that exceeded 1.2 g L−1 with lipid content exceeding 60%. Likewise, G4-9, which was also identified as Micractinium conductrix, and P2-15, which was identified as Choricystis parasitica, have lipid content which accounted for 89.10% and 57.48%, respectively; although their biomass was lower. The percentage of fatty acid methyl esters of the four microalgae achieved >60–80%; thus, meeting the standard of biodiesel properties. Therefore, the microalgae isolates have great potential for being developed as biodiesel feedstock.

Microplastics are contaminants in the form of tiny plastic fragments diluted in terrestrial and aquatic environments. Recently, these contaminants have become a concern due to their negative impact on the quality of life of living things. The isolation and examination of microplastic degrading microorganisms' ability from two large mature landfills were conducted. Therefore, this study aims to obtain bacteria and fungi as bioremediation agents that can degrade microplastics. The isolation process was conducted by direct and indirect (enriched) methods. Nutrient agar and potato dextrose agar media were used either in the form of a full or a tenth of a recipe with the addition of polyethylene, polypropylene, and polystyrene microplastics. Furthermore, indirect isolation used mineral media treated with the same microplastics. Colony morphology was observed to be the difference among isolates. The isolates were selected based on their ability to produce lipase in butter agar, and their ability to use microplastic as the only carbon source was examined. A total of 211 isolates were obtained, consisting of 74 bacteria and 137 fungi. One-third of the total isolates produced lipase. A bacterial isolate with the highest lipase index identified based on the 16S rRNA gene showed that it was Bacillus paramycoides. The isolate used all three types of microplastics, with the highest ability in polystyrene, which was degraded up to 11.12% in 42 days. In conclusion, microorganisms isolated from the landfill leachate have potential as bioremediation agents that degrade microplastics. Keywords: Bacillus, Bacillus paramycoides, Biodegradation, Bioremediation, Landfill, Leachate, Microplastics, Polystyrene