# Microbial transformation of sewage sludge to biolipid-based fuel using potential oleaginous bacteria Streptomyces sp

## TL;DR

This paper explores using Streptomyces bacteria to convert sewage sludge into biolipids for biofuel production, offering a sustainable waste-to-energy solution.

## Contribution

The study introduces Streptomyces sp. as a novel oleaginous bacterium for converting sewage sludge into biolipids for biofuel.

## Key findings

- Streptomyces sp. achieved 40% lipid accumulation in dry cell biomass under optimized conditions.
- FTIR and GC–MS confirmed the presence of palmitic and oleic acids in the extracted biolipids.
- The biolipids were successfully transesterified into biofuel, demonstrating dual benefits of waste reduction and energy production.

## Abstract

The high proportion of sludge generation worldwide has sparked interest in utilizing it for alternative purposes. Among different potential applications, using sludge as a substrate for oleaginous bacteria is a relatively novel approach. The study was conducted to harness Streptomyces sp. to produce bio-lipids and their further processing for biofuel through transesterification.

Sewage sludge was obtained from the I-9 treatment plant, Islamabad; after initial characterization the unprocessed sludge was optimized viz.: incubation time (24–96 h), inoculation rate (5–15%), pH levels (4–9), temperature (25–40°C), agitation (0–250 RPM), nitrogen sources (yeast, urea, ammonium chloride, and ammonium nitrate), and carbon sources (glucose, sucrose, starch, and dextrose). The qualitative analysis of the stored bio-lipids was performed using Fourier-transform infrared spectroscopy (FTIR) and Gas Chromatography Mass Spectrometry (GC–MS).

The maximum reactor performance was achieved with 40% lipid accumulation (gravimetric basis) in the dry cell biomass of Streptomyces sp. The results indicated the presence of C-H (Alkane), with additional phenolic and alcoholic bonds through FTIR, whereas the GC–MS results indicated the presence of palmitic acid and oleic acid as the most recurring compounds. This highlights the strong potential of Streptomyces sp. for biolipid based fuel production using sludge as a substrate. The contents of the extract (i.e., bio-lipids) were successfully transesterified to produce biofuels from the stored lipids. The findings indicated that the use of Streptomyces sp. potentially provides a dual benefit of reducing organic loading from the sludge along with biofuel production under optimized reactor conditions.