Abstract
Pink pigmented facultative methylotrophic (PPFM) bacteria are ecologically distributed microorganisms. They have been isolated in many types of ecosystems like soil, water, air, in association with plants and even as pathogens in humans. However, a yet unexplored area for PPFM bacteria research is in food. Hence, the objective of this study was to establish the presence of PPFM bacteria in Philippine fermented food, in particular shrimp paste, and characterise them phenotypically and genotypically. A total of 13 PPFM bacteria were obtained from Philippine shrimp paste. Sequencing of the 16S rRNA gene revealed that the PPFM bacterial isolates belong to the genus Methylobacterium. A total of 35 phenotypic characterisations were performed that included morphological, biochemical and physiological tests. Phylogenetic tree was constructed to establish the genetic relatedness of the isolates. Morphological test results showed that all 13 isolates were consistent with the established phenotypic characters of the genus such as pink colony colour, Gram negative and rod-shaped. Biochemically, the use of API® 20 NE tests showed heterogeneity of results and physiological tests exhibited that the isolates are primarily mesophilic and halotolerant, being able to grow at 2% salt. Phylogenetic analysis showed that the isolates are Methylobacterium populi, M. dankookense, M. lusitanum, M. radiotolerans and M. zatmanii. This study confirmed the presence and diversity of PPFM bacteria in Philippine shrimp paste. Further studies are needed to show the functional activity of Methylobacterium in Philippine shrimp paste production.
Highlights
IntroductionFermentation is one of the oldest forms of food preservation technology in the world (Aloys & Angeline 2009)
It constitutes an essential contribution to human diets in many countries because it is an inexpensive way of preserving and improving food nutritional value while enhancing sensory properties (Gadaga et al 1999). It is the desirable process of biochemical modification of food products brought about by microorganisms and their enzymes that may lead to the detoxification and destruction of undesirable factors present in raw food like tannins and polyphenols
All isolates were facultative methylotrophic as they have initially shown to grow in a medium with reduced carbon source (AMS + 0.5% methanol) followed by a multi-carbon medium using glycerol-peptone agar (GPA) for purification
Summary
Fermentation is one of the oldest forms of food preservation technology in the world (Aloys & Angeline 2009). It constitutes an essential contribution to human diets in many countries because it is an inexpensive way of preserving and improving food nutritional value while enhancing sensory properties (Gadaga et al 1999) It is the desirable process of biochemical modification of food products brought about by microorganisms and their enzymes that may lead to the detoxification and destruction of undesirable factors present in raw food like tannins and polyphenols. The Philippines has produced several fermented products like nata de coco (coconut gel), buro (fermented rice with fish), puto (acid-fermented leavened bread) and atchara (fermented pickled Carica), among others Some of these products are even exported to other countries such as shrimp paste or more vernacularly known as bago-ong that constitutes 42% of the total Philippine exported processed food. Just like other fermented food products, the microbiology of shrimp paste is quite complex and largely unknown (Blandino et al 2003)
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