Pichia kudriavzevii as feed additive in Nile tilapia (Oreochromis niloticus) diet.

Yeasts are unicellular eukaryotic microorganisms extensively employed in various applications, notably as an alternative source of protein in feeds, owing to their nutritional benefits. Despite their potential, marine and mangrove yeast species used in the aquaculture industry have received little attention in the Philippines. Pichia kudriavzevii (A2B R1 ISO 3), sourced from bark samples, was selected and mass-produced due to its high protein content and amino acid profile. The dried biomass of P. kudriavzevii was incorporated into the diets of Nile tilapia (Oreochromis niloticus) juveniles at varying inclusion levels (0, 1, 2, and 4 g/kg diet) and its effect on their growth performance, body composition, and liver and intestinal morphology was assessed after 40 days of feeding. The groups that received P. kudriavzevii at a concentration of 2 g/kg diet exhibited higher final body weight, percent weight gain, and specific growth rate in comparison to the other treatment groups. Whole body proximate composition did not vary among the dietary groups. Intestinal and liver histopathology also indicated no abnormalities. These findings suggest the potential of ascomycetous P. kudriavzevii as a beneficial feed additive in Nile tilapia diets, warranting further investigation into its long-term effects and broader applications in fish culture.

Growth and fatty acid profiles of Halophytophthora vesicula and Salispina spinosa from Philippine mangrove leaves.

Studies on marine-sourced fatty acids have gathered significant interest recently as an important component of aquaculture feeds and of biofuel production. Of the organisms capable of producing fatty acids, marine oomycetes are promising model organisms. One group of marine oomycetes are the Halophytophthora spp. which is known to have an important role in leaf decomposition, thereby changing the plant debris into exudates which are usable to consumers in the mangrove ecosystems. This study reports the three mangrove oomycetes isolated from Philippine mangrove forests, identified herein as Halophytophthora vesicula AK1YB2 (Aklan), H. vesicula PQ1YB3 (Quezon) and Salispina spinosa ST1YB3 (Davao del Norte). These isolates were subjected to growth analyses using varying incubation parameters (salinity level and pH), and for fatty acid production. Results revealed the presence of different fatty acids such as Arachidonic acid, Linoleic acid and Vaccenic acid when grown on V8S and PYGS media. This study is the first observation of fatty acids from S. spinosa and H. vesicula from the Philippines. SIGNIFICANCE AND IMPACT OF THE STUDY: Tropical Philippines straddling west of the Pacific Ocean and East of South China Sea is rich in marine and estuarine oomycetes. These micro-organisms, hitherto poorly known and unstudied in the country, play an important role in the nutritive cycle of the mangrove ecosystem. Due to the increasing demand for an alternative source of fatty acids, species of Oomycetes isolated from select mangrove forests in Luzon, Visayas and Mindanao were analysed for their fatty acid contents. Prospects for industrially-important fatty acids make these Oomycetes all-important to study in applied microbiology in the Philippine setting where these structurally simple micro-organisms abound.

Microbial demetallization of crude oil: nickel protoporphyrin disodium as a model organo-metallic substrate.

A soil isolate designated as YA-1 strain was selected for its ability to degrade nickel protoporphyrin disodium (NiPPDS). The strain was capable of utilizing NiPPDS as the sole source of carbon. This strain, a gram-negative aerobic rod, was identified as Pseudomonas azelaica YA-1 based on the result of its 16S rRNA analysis. Product analyses by HPLC showed that this strain can decompose the porphyrin ring to which a metal ion is bound. However, the use of whole bacterial cells cannot result in extensive NiPPDS degradation; therefore, the YA-1 enzyme was extracted and purified. This NiPPDS-degrading enzyme named as protoporphyrinase was purified from P. azelaica YA-1 by ammonium sulfate fractionation and sequential chromatographies using DEAE Toyopearl 650 M, CM Toyopearl 650 M and Biogel P-60 columns, with a yield of 11.3% based on the enzyme activity and an overall purification of 498-fold. The molecular weight of this enzyme is estimated to be 39,000 Da by SDS-PAGE and 34,000 Da by gel filtration. The optimum pH and temperature for the enzyme were 7.0 and 30 degrees C, respectively. The activity was stable at pH 2.0-11.0 and at temperatures below 50 degrees C. The enzyme activity was inactivated by ferric chloride, potassium ferricyanide, ZnCl2 and CdCl2.