Page 109 - EER-2-3

Explora: Environment
and Resource Enzymatic degradation

2.5. Physicochemical analysis of LDPE degradation with the LDPE samples at 50% and 100% concentrations.

2.5.1. Determination of dry weight of residual LDPE At 50% Lip concentration, the weight reduced from 0.0036
to 0.0035 g (day 10) and 0.0034 g (day 30), corresponding
To obtain the dry weight of residual LDPE, the LDPE to 2.78% and 5.56% LDPE weight loss, respectively,
films were extracted from the degradation medium and thereby indicating greater degradation over time. The
cleaned using a 70% ethanol solution, followed by rinsing 100% enzyme concentration observed a higher percentage
with distilled water. The purified LDPE films were allowed weight loss compared to the 50% enzyme concentration;
to air-dry to a constant weight. The percentage of weight for instance, the Lac enzyme system reported 5.13% and
reduction was calculated using Equation I. 51 8.33% weight loss at 50% and 100% Lac concentration,
respectively, after 30 days. Likewise, Liu et al. recorded
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Initial sample Final sample
Percent weight − weight a weight loss of 8.9% and 11.8% for LDPE films at day 7.
weight = Initial weight × 100 (I) In terms of degradation efficiency, LDPE incubation
( )
loss % in 100% Lip, 100% Lip-Lac, and 100% Lac recorded
11.11%, 15.21%, and 8.33% weight loss, respectively. This
2.5.2. Scanning electron microscopy (SEM) observation is relatively consistent with the 10.15% loss
reported by Mazaheri and Nazeri with Stenotrophomonas
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Following weight analysis, the LDPE samples were cut into spp. enzymes. This implies that LDPE was more effectively
5 mm fragments. To observe the surface morphology of the degraded by the Lip-Lac enzyme system, suggesting that
LDPE, SEM (SU3800/SU3900, Hitachi High-Tech, Japan) while Lip alone exhibits notable degradation efficiency,
was employed. Each sample was carefully mounted onto the Lip-Lac enzyme system has much higher degradation
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a specimen holder (stub) to ensure proper placement and efficiency. In addition, higher enzyme concentrations
fit within the SEM chamber, with all fragments trimmed to enhance the degradation efficiency, as observed from
suitable dimensions for imaging. Table 1. Our findings corroborated that of Kunlere et al.,
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who used A. flavus to degrade LDPE. Concentrations
3. Results and discussion below 50% are likely to result in even lower degradation
3.1. Effect of enzyme concentration on LDPE rates. Given that 50% concentration already yields modest
degradation weight loss (e.g., 5.56% in the Lip system), reducing
the concentration further would likely diminish the
After incubation of LDPE in 50% and 100% enzyme degradation efficiency, making it less effective for practical
concentrations for 10 and 30 days, the weight of the residual purposes. Increasing the incubation period beyond 30 days
samples was measured (Table 1). The initial weight and size may further enhance degradation, as the enzymes have
of the material influence degradation. Smaller particles more time to act on the material. Conversely, reducing the
have a higher surface area-to-volume ratio, facilitating incubation time might not allow for sufficient degradation,
better enzyme interaction and, consequently, higher leading to lower weight loss percentages. Therefore, longer
degradation rates. Therefore, reducing the initial size incubation periods are generally favorable for improved
of the material can enhance the degradation process. As degradation. Yao et al. reported a high weight loss on
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displayed in Table 1, Lip and Lac enzymes were incubated
day 30 for their LDPE film samples. Similarly, in this
Table 1. Percentage weight loss of LDPE samples at different study, optimal degradation was observed on day 30 across
enzyme concentrations all systems. For instance, the Lip-Lac system at 100%
concentration reported weight loss of 15.21% on day 30
Enzyme Concentration Initial Final weight Weight loss compared to 6.52% on day 10. This indicates that prolonged
(%) weight (g) (%) exposure of LDPE to the enzyme system enhances the
(g) Day Day Day Day degradation process. In a previous study, untreated
10 30 10 30 LDPE reported a weight loss of 38.82% using a combined
Lip 50 0.0036 0.0035 0.0034 2.78 5.56 system of Lip, Lac, esterase, and manganese peroxidase.
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100 0.0036 0.0034 0.0032 5.56 11.11 Figures 1-4 illustrate the relationship between enzyme
Lip-Lac 50 0.0043 0.0041 0.0039 4.65 9.30 concentration and LDPE weight loss, as derived from the
100 0.0046 0.0043 0.0039 6.52 15.21 data in Table 1.
Lac 50 0.0039 0.0039 0.0037 0.00 5.13 A high weight loss denotes effective biodegradation,
100 0.012 0.012 0.011 0.00 8.33 indicating that the material is efficiently broken down by
Abbreviations: Lac: Laccase; LDPE: Low-density polyethylene; Lip: the enzymes. Conversely, a low weight loss suggests limited
Lipase. degradation, which may be inadequate for practical

Volume 2 Issue 3 (2025) 4 doi: 10.36922/EER025220042