Low daily calcium intake in Asia, especially in Indonesia, is still a serious problem. The abundant fish bone waste from the fishery fillet industries in Indonesia,  can be employed as an alternative source of calcium to meet daily calcium needs. This research aimed to determine which of the six fish species (tilapia, catfish, grouper, snapper, tuna, kingfish mackerel) produces the best quality and the most cost-effective nano-calcium powder for a recommendation to the stakeholders. The calcium was extracted using an alkali treatment. The properties of the produced nano-calcium powders were analyzed for: proximate composition, calcium and phosphorus levels, color brightness level, XRD, FTIR, particle size, and SEM-EDX image analysis. The tilapia bone had the finest particle size of calcium (87.37 nm), while the grouper bone had the biggest particle size (281.4 nm). The brightness of all yields varied from 83.83 (beige-kingfish mackerel) to 90.64 (white-tilapia). The average calcium content from EDX analysis varied from 21.51% (snapper) to 34.37% (grouper). The average phosphorus levels ranged from 10.73% (kingfish mackerel) to 15.99% (grouper). The EDX Ca/P molar ratio was 1.41-1.66 across all samples. The FTIR spectra showed that all samples contained PO, CH, CO, NH, and OH groups. The XRD spectra pattern determined that the two main components of the fish bone nano-calcium powder were 90% hydroxyapatite and halite. All fish bone samples have the potential to be used as raw material for nano-sized calcium. However, grouper bone with the highest calcium content and the highest nano-calcium yield was the best choice for further study.

This study selected bacteria with high anti-Candida albicans (CA) activity among ten bacteria isolated from marine sponges. Bacteria were cultivated using the basal medium to produce the extract. Minimum Inhibitory Concentration (MIC) microdilution broth was used as an anti-CA assay followed by TLC-direct bioautography to characterize their active compound with spray reagents. The bacteria determination was done by molecular approaches using Repetitive-Element Sequences-based-PCR (rep-PCR) and amplification of 16S rDNA partial gene sequences, continued with BLAST analysis. The four out of ten tested bacteria had high anti-CA compounds and were potentially to be produced on a larger scale using the basal medium, which was BYT5C4, BYT5C5, BYT1A, and BYT7, with MIC of 1 mg/mL against 7.5×106 CFU/mL CA. TLC-bioautography test results showed that all metabolites from each isolate had different Rf and types of metabolites. Rep-PCR test showed that four bacteria had a low similarity index, indicating that they were different species. Based on molecular identification results, the BYT5C4, BYT5C5, BYT1A, and BYT7 isolates are strictly related to Brevibacterium casei, Exiguobacterium profundum, Micrococcus lylae, and Bacillus firmus, respectively. The active metabolites identified in this study can be isolated to determine the active molecules and their inhibitory routes to fungal growth. It is worth noting that additional research might be conducted to compare the activity of each antifungal metabolite to the synergistic activity of numerous antifungal metabolites detected in plant extracts.

Highlight Research Autoclaving for 3x3 hours followed by alkaline hydrolysis (3x3AH) may lower nano-calcium particle size into 47.47 nm 3x3AH sample contain 30.73% calcium and 18.37% phosphorus 3x3AH sample created the best calcium solubility (26.14 %) in comparison to synthesized CaCO3 (14.34 %) Grouper nano-calcium powder includes trace quantities of organic content, such as protein and fat, which enhance calcium's solubility.   Abstract Fish bone nano-calcium production may solve two challenges, providing calcium for lactose-intolerant people and recycling bone waste. Fish bone autoclaving prior to extraction reduces fat, denatures collagen, and softens bones but only few researches have compared autoclaving duration with nano-calcium product quality, particle size, and its solubility in in vitro testing. This study studied the influence of autoclaving duration followed by alkaline hydrolysis on nano-calcium characteristics to enhance calcium solubility in in vitro gastrointestinal simulation experiments. The dried grouper (Epinephelus sp.) bone was divided into four groups: 0A (no autoclaving), 3A (3 h autoclaving), 2x3A (double cycle for 3 h autoclaving), and 3x3A (triple cycle for 3 h autoclaving). Each group was followed by alkaline hydrolysis, designated as 0AH, 3AH, 2x3AH, and 3x3AH. The results showed that autoclaving for 3x3 hours followed by alkaline hydrolysis resulted in lowest nano-calcium particle size of 47.47 nm consisting of 30.73% calcium and 18.37% phosphorous. 3x3AH sample created the best calcium solubility (26.14%) in comparison to synthesized CaCO3 (14.34%). In contrast to synthetic CaCO3, grouper nano-calcium powder includes trace quantities of organic contents, such as protein and fat, which enhance calcium solubility. In vivo research should be established to study the bioavailability and influence of grouper nano-calcium powder on bone density.