Enzyme immobilization is a powerful method to improve the stability, reuse, and enzymatic properties of enzymes. The immobilization of the α-amylase enzyme from Aspergillus fumigatus on a chitin-bentonite (CB) hybrid has been studied to improve its stability. Therefore, this study aims to obtain the higher stability of α-amylase enzyme to reduce industrial costs. The procedures were performed as follows: production, isolation, partial purification, immobilization, and characterization of the free and immobilized enzymes. The CB hybrid was synthesized by bentonite, chitin, and glutaraldehyde as a cross-linker. The free enzyme was immobilized onto CB hybrid using 0.1 M phosphate buffer pH 7.5. The free and immobilized enzymes were characterized by optimum temperature, Michaelis constant (K_M), maximum velocity , thermal inactivation rate constant (k_i), half-life (t_1/2), and transformation of free energy because of denaturation (ΔG_i). The free enzyme has optimum temperature of 55°C, K_M = 3.04 mg mL⁻¹ substrate, , k_i = 0.0171 min⁻¹, t_1/2 = 40.53 min, and ΔG_i = 104.47 kJ mole⁻¹. Meanwhile, the immobilized enzyme has optimum temperature of 60°C, K_M = 11.57 mg mL⁻¹ substrate, , k_i = 0.0045 min⁻¹, t_1/2 = 154.00 min, and ΔG_i = 108.17 kJ mole⁻¹. After sixth cycle of reuse, the residual activity of the immobilized enzyme was 38%. The improvement in the stability of α-amylase immobilized on the CB hybrid based on the increase in half-life was four times of the free enzyme.

The stability of the α-amylase enzyme has been improved from Aspergillus fumigatus using the immobilization method on a bentonite matrix. Therefore, this study aims to obtain the higher stability of α-amylase enzyme from A. fumigatus; hence, it is used repeatedly to reduce industrial costs. The procedures involved enzyme production, isolation, partial purification, immobilization, and characterization. Furthermore, the soluble enzyme was immobilized using 0.1 M phosphate buffer of pH 7.5 on a bentonite matrix, after which it was characterized with the following parameters such as optimum temperature, Michaelis constant (K_M), maximum velocity , thermal inactivation rate constant (k_i), half-life (t_1/2), and the change of energy due to denaturation (ΔG_i). The results showed that the soluble enzyme has an optimum temperature of 55°C, K_M of 3.04 mg mL⁻¹ substrate, of 10.90 μmole mL⁻¹ min⁻¹, k_i of 0.0171 min⁻¹, t_1/2 of 40.53 min, and ΔG_i of 104.47 kJ mole⁻¹, while the immobilized enzyme has an optimum temperature of 70°C, K_M of 8.31 mg mL⁻¹ substrate, of 1.44 μmole mL⁻¹ min⁻¹, k_i of 0.0060 min⁻¹, t_1/2 of 115.50 min, and ΔG_i of 107.37 kJ mole⁻¹. Considering the results, the immobilized enzyme retained 42% of its residual activity after six reuse cycles. Additionally, the stability improvement of the α-amylase enzyme by immobilization on a bentonite matrix, based on the increase in half-life, was three times greater than the soluble enzyme.

Pineapple litter has a complex polymer of cellulose, hemicellulose, and lignin, which makes them difficult to decompose. However, pineapple litter has great potential to be a good organic material source for the soil when completely decomposed. The addition of inoculants can facilitate the composting process. This study investigated whether the addition of cellulolytic fungi inoculants to pineapple litters improves the efficiency of the composting processes. The treatments were KP1 = pineapple leaf litter: cow manure (2:1), KP2 = pineapple stem litter: cow manure (2:1), KP3 = pineapple leaf litter: pineapple stem litter: cow manure P1 (leaf litter and 1% inoculum), P2 (stem litter and 1% inoculum), and P3 (leaf + stem litters and 1% inoculum). The result showed that the number of Aspergillus sp. spores on corn media was 5.64 x 10⁷ spores/mL, with viability of 98.58%. Aspergillus sp. inoculum improved the quality of pineapple litter compost, based on the enhanced contents of C, N, P, K, and the C/N ratio, during the seven weeks of composting. Moreover, the best treatment observed in this study was P1. The C/N ratios of compost at P1, P2, and P3 were within the recommended range of organic fertilizer which was 15–25%, with a Carbon/Nitrogen proportion of 11.3%, 11.8%, and 12.4% (P1, P2, and P3), respectively.

Pineapple plantations leave a lot of plant biomass after the planting season ends. The abundant residue of pineapple plants causes problems due to the high content of lignocellulose, which is difficult to decompose naturally. This study aimed to isolate and characterize lignocellulolytic microfungi isolates from pineapple plantations. The information of this study was used as data to prepare an inoculum for the induction of pineapple litter composting that was resistant to stress to pineapple plantation habitat. The results showed that there were 11 dominant lignocellulolytic microfungi isolates found from pineapple litter and plantation soil. Using selective media, the selection showed five cellulolytic (Bioggp 3, 6, 9, 11, and 12); five xylanolytic (Bioggp 3, 6, 8, 9, and 12); and two ligninolytic microfungi isolates (Bioggp 2 and 5). Bioggp 3, 6, 9, and 12 are cellulolytic and xylanolytic with Bioggp 3 showing the highest cellulolytic index (4.0) and xylanolytic index (4.20). Testing of ligninolytic microfungi showed that the Bioggp 5 isolate had a stronger lignin indicator (color intensity=4.0 and zone ratio of 1.47) than the Bioggp 2 isolate. Bioggp 9 had the highest cellulolytic isolate spore productivity at 4.5×10⁸ spores/mL with 93.3 spore viability, and Bioggp 3 had the highest xylanolytic isolate spore productivity at 2.5×10⁹ spores/mL with 89.3 spore viability. Bioggp 2 had the highest ligninolytic isolate spore productivity at 1.8×10⁹ spores/mL, but Bioggp 5 showed the highest spore viability at 98.0.

A new dimer of natural isoflavonoid along with some known flavonoid compounds was successfully isolated from the roots of Indonesian Sesbania grandiflora plant using ethyl acetate extraction. The new compound specified as naturally bi-isoflavonoid with (4→6) inter-isoflavanyl linkage and four known flavonoids xenognosin B, liquiritigenin, 7,2′4′-trihydroxyisoflavone, demethylvestitol, and 1,1′-bi-2-naphthol was isolated and the antituberculosis activity of the compounds was studied. The structure of all compounds was elucidated with the aid of 1D and 2D NMR, UV spectroscopy, and HRESI mass spectrometry. The data obtained were also compared with the previous published data. Among compounds, 1,1′-bi-2-naphthol was found to exhibit the highest activity against Mycobacterium tuberculosis H37Rv with the MIC’s value of 10.9 µM while the biisoflavonoid with (4→6) inter-isoflavanyl linkage showed moderate activity with the MIC’s value of 92.2 nM, compared with isozianid as a positive control with the MIC’s value of 0.569 nM. It is worth to note that 1,1′-bi-2-naphthol and biisoflavonoid with (4→6) inter-isoflavanyl linkage were isolated for the first time from a natural source. Both compounds have been previously reported as synthetic compounds, which is synonymous with 3,4- trans-4-[(3S)-7,2′-dihydroxy-4′-methoxyisoflavan-6-yl]-7,2′-dihydroxy-4′-methoxyisoflavan and 1,1′-bi-2-naphthol, respectively. In this respect, the results of this study suggest that the roots of S. grandiflora is a potential source of new natural product compounds, with promising bioactivities.