Jurnal Natural

Morphological and Biochemical Characterization of PGPR Isolates from Elephant Grass (Pennisetum purpureum)

Tue, 30 Jun 2026 00:00:00 +0000

Intensive and prolonged use of inorganic fertilizers in Indonesia remains predominant among farmers; however, it can lead to soil contamination and reduced fertility over time. Biofertilizers provide a sustainable alternative, with Plant Growth-Promoting Rhizobacteria (PGPR) serving as key components naturally associated with plant roots. This study aimed to isolate and characterize PGPR from the roots of elephant grass (Pennisetum purpureum) collected from Amban Pantai Manokwari- West Papua. Isolation procedures involved preparing PGPR starters, purifying colonies, and conducting macroscopic and microscopic observations along with biochemical tests. Macroscopic analysis revealed six isolates with white colonies; shapes were circular (PGPR 1 and 5) or irregular (others); elevations included convex, raised, flat, and umbonate; margins were undulate or rhizoid; and oxygen requirements ranged from aerobic, obligate aerobic, anaerobic, to facultative anaerobic. Microscopically, all isolates were rod-shaped and motile, with Gram-positive (PGPR 2 and 3) or Gram-variable (PGPR 1, 4, 5, and 6) characteristics.

Biochemical assays indicated positive sucrose fermentation (all isolates, though partial in some), lactose and dextrose fermentation (mainly PGPR 1 and 3), gelatin hydrolysis (PGPR 1, 3, and 5), citrate utilization (PGPR 5), MR positivity (all isolates), VP positivity (PGPR 2 and 4), H₂S production (only PGPR 4), negative indole, and absence of gas production. These findings demonstrate significant morphological and metabolic diversity among the isolated PGPR, underscoring their potential as biofertilizer candidates for sustainable agriculture in tropical regions such as West Papua. The characterization analysis revealed that the isolates belong to the genera Bacillus (PGPR 1, 2, 3, 5, 6) and Enterobacter (PGPR 4).

Characteristics of Briquettes Produced from Corn Cob and Corn Stalk Charcoal Blends

David Mangallo, Thomas Pagasis, Bertha Mangallo — Tue, 07 Jul 2026 12:16:23 +0000

Corn cobs and corn stalks represent abundant agricultural residues with significant potential for conversion into solid biofuels. This study aimed to evaluate the physicochemical characteristics of briquettes produced from varying proportions of corn cob charcoal and corn stalk charcoal. Carbonization was conducted through pyrolysis using a modified oil-drum reactor. The resulting char was pulverized and sieved to 60 mesh to ensure particle uniformity prior to briquetting. A 5% tapioca starch solution was used as a binding agent, and briquettes were formed using a hydraulic press in a honeycomb configuration (4-inch diameter, 16 central perforations). Five different charcoal composition ratios were prepared and analyzed. Proximate analysis revealed moisture content ranging from 4.68% to 5.71%, ash content from 12.27% to 17.23%, volatile matter from 16.24% to 21.62%, and fixed carbon from 56.47% to 65.78%. The calorific value varied between 5,138 and 5,274 cal/g. The results demonstrate that blended corn cob and corn stalk charcoal briquettes exhibit favorable fuel properties and potential applicability as sustainable alternative energy sources.

Nutritional Profile of Awyu and Yaqai Girls in Mappi Regency, South Papua

Marice Dou, Febriza Dwiranti, Elda Irma Jeanne Joice Kawulur — Thu, 09 Jul 2026 16:03:06 +0000

ABSTRACT

Nutritional status is a condition determined by the extent to which the body’s physiological needs for energy and nutrients are met through dietary intake. Primary school age is a critical period for physical growth, cognitive development, and the maturation of organ systems. Nutritional imbalance during this stage may have long-term consequences, including stunting, reduced immune function, and impaired brain development. The aim of this study was to examine the body growth patterns of Awyu and Yaqai girls. This study used a cross-sectional design. Physical growth status was assessed in 163 girls aged 6–12 years at the primary school level, consisting of 84 Awyu girls and 79 Yaqai girls in Mappi Regency, South Papua Province. Nutritional status was determined using the body mass index-for-age (BMI-for-age) index based on anthropometric measurements, including height (cm) and weight (kg), as well as interviews. The results showed that the nutritional profiles of girls from both ethnic groups were not substantially different. Most of the children had a good nutritional status, with 98 children (98.15%) classified as normal, 2 children (1.22%) were classified as overweight, and none were classified as thinness and obese.

Keyword : Mappi, girl, cross-sectional, nutritional status

Development and Performance Test of Vertical Stirrer Rotary Blade Type of Sago Starch Extraction Machine Powered by Gasoline Engine

Darma Darma, Reniana Reniana, Risma Uli Situngkir, Arens T. Solissa — Mon, 20 Jul 2026 06:34:10 +0000

Sago starch extraction is aimed to separate starch as much as possible from waste or fibre. The efficiency and effectiveness of extraction process depend on several factors i.e. the characteristics of extraction machine and fineness degree of disintegrated sago pith is being processed. In previously study, it had been resulted stirrer rotary blade type of sago starch extraction machine powered by gasoline engine. The purpose of this study was to develop and test the performances of stirrer rotary blade type of sago starch extractor. The developed machine was tested it’s performances under 4 levels of extraction duration time i.e. 10 minutes, 15 minutes, 20 minutes and 25 minutes. The Parameter have been measured to evaluate the machine’s performances were (1) extraction capacity, (2) starch rendement, (3) starch yield and (4) starch losses in sago pith waste. Based on performance test results have shown that the developed machine has higher performance than previously prototype. The results showed that extraction duration time significantly affect extraction capacity, starch rendement, and starch losses in sago pith waste, however the starch yield was not affected significantly. The highest performance was resulted at extraction duration time 15 minutes. The performances of the machine at the condition were (1) extraction capacity 247 kg repos/hour, (2) starch rendemen 37,35%, (3) starch yield 78,81 kg/hour, and (4) starch losses in sago pith waste 2,00%.

DYNAMICAL ANALYSIS OF A PREDATOR-PREY MODEL WITH A MULTIPLICATIVE ALLEE EFFECT ON THE PREY AND A STRUC-TURED PREDATOR POPULATION DIVIDED INTO SUSCEPTIBLE AND INFECTED CLASSES

Thu, 30 Jul 2026 07:08:55 +0000

This study examines the interaction between prey and predator populations by incorporating a multiplicative Allee effect on the prey and disease infection in the predator. The mathematical model is constructed using a system of differential equations that integrates logistic prey growth, Holling type II functional response, and compartmental dynamics of healthy and infected predators. The analysis was carried out through nondimensionalization, linearization, and equilibrium point determination using the Jacobian matrix to investigate the local stability of the system. The results indicate that the system possesses several equilibrium points representing population extinction, prey-only existence, and coexistence of prey with either healthy or infected predators. The stability of these equilibria is strongly influenced by parameters such as the prey intrinsic growth rate, the Allee threshold, and the disease transmission rate. Numerical simulations demonstrate that the Allee effect can drive the prey population to extinction when its size falls below a critical threshold, while the disease in predators reduces the growth of healthy predators and thus contributes to the persistence of the prey population. This research enriches the field of mathematical ecology by providing new insights into the role of Allee effects and epidemiology in predator-prey dynamics.

Integrasi Penginderaan Jauh dan Sistem Informasi Geografis Untuk Analisis Suhu Permukaan Daratan di Kabupaten Manokwari.

Novita Kosamah, Abdul Muis Muslimin, Aries Astradhani Subgan — Fri, 31 Jul 2026 13:35:19 +0000

The development of urban areas in Manokwari Regency has the potential to reduce the availability of land containing vegetation or Green Open Space (GOS) which may be a contributing factor to increasing land surface temperature that triggers the Urban Heat Island (UHI) phenomenon. This study aims to estimate land surface temperature, analyze its relationship with land cover, and examine the pattern of temperature distribution in the four districts of the study area. The research method integrates remote sensing and Geographic Information Systems, using Landsat 8 OLI/TIRS imagery data, topographic maps, and land cover maps, which were analyzed in GIS through an overlay method and supported by field surveys. The results show that land surface temperatures range from 18.29–30.79°C with an average of 23.23°C and are dominated by the 25–30°C temperature class. Areas with extensive vegetation cover have lower temperatures, whereas residential and built-up areas have higher temperatures. Field surveys at 49 points indicate an average air temperature of 36.25°C with a low correlation to Landsat-derived temperatures (r = 0.34). The areal distribution of high temperatures is, in sequence: West Manokwari District, 2,201.560 ha (28.517%); South Manokwari District, 1,514.092 ha (5.891%); East Manokwari District, 413.156 ha (15.866%); and North Manokwari District, 184.431 ha (0.982%). West Manokwari District is the top priority for mitigating increasing land surface temperature, followed by East Manokwari District and South Manokwari District, through the development of GOS in built-up areas in Manokwari Regency.