Safety Disposal of Rice Straw by Biodegradation Using Streptomyces Tendae

Fahad Al-Dhabaan

doi:10.3390/su132413640

Abstract

Rice straw is a byproduct formed during rice cultivation. Disposal of rice straw may happen via unhygienic methods such as burning, which is happening in Malaysia and other countries. This study aims to rid rice straw via an eco-friendly biodegradation technique. Biodegradation of rice straw depended on actinobacteria, which were isolated from the cultivated soil of rice and rhizosphere areas in Tabuk region. Out of thirty actinobacterial isolates, only three isolates (S-5, S-12, S-20) biodegraded starch, cellulose, lignin and rice straw powder. The most potent actinobacterial isolate (S-5) was identified as Streptomyces tendae, which effectively biodegraded all polysaccharides of rice straw. Biodegradation of rice straw was associated with a significant reduction in C/N ratio, where the latter fell from 30.4% to 17.2% within 42 d.

Highlights

Actinobacteria are sporulating, aerobic, and Gram-positive microorganisms, which are characterized by a high G + C content [1,2]
Nigam and Singh [32] reported that recalcitrant substrates such as starch, cellulose and lignin were completely degraded by the hydrolytic enzymes of actinobacteria
Bacterial identification was confirmed by 16S rRNA gene sequencing using the PCR technique, which revealed that 98% similarity, as shown in Figure 2, was observed between the actinobacterial isolate (S-5) and S. tendae M23 with accession number HM594286.1 in GenBank [33]

Summary

Introduction

Actinobacteria are sporulating, aerobic, and Gram-positive microorganisms, which are characterized by a high G + C content [1,2]. Actinobacteria are widely used in various industries, including the biotransformation industry due to its production of different bioactive metabolites such as lignocellulases [5]. Lignocellulases is a set of hydrolytic enzymes including amylases, cellulases, hemicellulases and lignolytic enzymes, which hydrolyze starch, cellulose, hemicellulose and lignin, respectively [6]. Cellulases are used in various industrial applications, such as bioethanol, biomethane, textile, pulp, paper and detergent industries [9,10,11]. Lignolytic enzymes are using as bioreactors in the biofuel, paper, textile, food, cosmetic and pharmaceutical industries as well as other applications such as wastewater treatment, bioremediation and organic synthesis [13]. Different microorganisms are produced for lignocellulases, actinobacteria are still the most potent producers [14,15]

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