ABSTRACT
Aims: Previously described as non-favorable-microbial habitat, peat swamp forest has its own features, which are extremely acidic, poor in nutrient, water-logged and anoxic environment where rate of decomposition of plant litters is quiet slow. Interestingly, current research has proven that there is diversity of microbial communities in this ecosystem. The main objective of this study is to isolate bacteria from Pekan peat swamp forest soil that play a role in the decomposition of plant litters through cultivation on different agar-based medium. The success of isolation of bacteria from this neglected habitat could open the opportunity in unleashing the specific role of bacteria in peat swamp plant litter degradation as well as potential biotechnological application of these bacteria in lignocellulose-related industry. Methodology and results: To mimic the peat condition that is low in nutrient and comprised of plant debris, M1 and peat agar supplemented with cellulose, glucose, lignin and xylan were used. Specifically, for the isolation of actinomycetes, dry and wet heat pre-treatments were applied to the soil samples. Then, the samples were cultivated on three different agars which were oatmeal agar as well as M1 and peat agar supplemented with glucose. Enrichment method was applied in the isolation of cellulase-producing bacteria. It was found that higher number of bacteria and actinomycetes were successfully isolated from peat agar, followed by oatmeal agar and M1. In fact, more actinomycetes were isolated from soil that was treated with wet heat pre-treatment compared to dry heat pre-treatment and on peat agar compared to M1 and oatmeal agar. This finding is promising, indicating that the application of peat water in the agar-based medium is useful to mimic the actual environment of peat swamp and increase the possibility to isolate indigenous bacteria. Primary screening of isolates from samples enriched with carboxymethyl cellulose (CMC) showed positive result of decolourisation zone on Azo-CM-Cellulose agar indicating the ability of isolates to degrade cellulose compound. Conclusions, significance and impacts of study: The study indicates the effectiveness of different culture media in successful isolation of bacteria including actinomycetes. Using the enrichment method, bacteria that are able to degrade cellulose compound was successfully isolated even though it is well known that plant litter degradation in the peat swamp environment happens at very slow rates.
Subject(s)
BacteriaABSTRACT
Aims: Research on lignin degradation capability is previously restricted exclusively to fungal enzymes. However, recent studies had successfully revealed several soil bacterial strains that were able to produce ligninolytic enzymes. These bacterial ligninolytic enzymes were claimed to be more specific in catalysing cleavage of certain linkages between phenolic units of lignin polymers as compared to fungal enzymes. The present study focuses on screening for ligninaseproducing bacteria isolated from South East Pahang Peat Swamp Forest (SEPPSF) soil using agar-based assay. Methodology and results: Thirteen isolates used in this study, which were selected based on distinctive colony morphology from our previous isolation work, showed decolourisation zone on Azure B plates screening. The ratio of decolourisation zones were measured to the ratio of the colony size and the biggest ratio was 2.22 by isolate AR1. Only 4 out of the 13 isolates were able to grow on lignin plates. Subsequently, the 4 isolates, AR3, AR8, AR10 and AR13 were tested on M1 agar supplemented with 3 ligninolytic enzyme indicator compounds which were tannic acid (TA), guaiacol and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) respectively. All four isolates showed growth on TA plates while only AR10 showed a clear brown coloration. An Intense reddish-brown colour formation was observed around the colony of isolates AR3 and AR10 on guaiacol plates while none exhibited green coloration around the colonies when tested on ABTS plates. Conclusions, significance and impacts of study: Isolate AR10 that was identified as Serratia sp. was perceived to be a potential ligninase-producer, though in-depth analysis has to be conducted in the future to determine the specific ligninolytic enzyme activities and characteristics. The application of different substrates is essential to investigate the ligninolytic potential and reaction of those bacterial enzymes towards different indicator compounds. This study is a preliminary endeavour concerning potential ligninolytic enzymes from bacteria as biocatalysts in various industrial processes. This is the first report on preliminary study for ligninolytic activities of soil bacteria from SEPPSF soil.