Arabica coffee is the most popular and best-selling type of coffee. During coffee fermentation, microorganisms are essential for the production of metabolites and volatile compounds that affect coffee flavor quality. This work aimed to study the mutation, selection, and characterization of the Wickerhamomyces anomalus strain YWP1-3 as a starter culture to enhance the flavor quality of Arabica coffee. The results revealed that six mutants could produce relatively high levels of the pectinase enzyme on pectin agar media and exhibited high activity levels, ranging from 332.35 to 415.88 U/ml in mucilage broth. Strains UV22-2, UV22-3, UV41-1 and UV32-1 displayed higher levels of amylase activity than did the wild type. The UV22-2 and UV22-3 mutants exhibited the highest pectin degradation indices of 49.22% and 45.97%, respectively, and displayed significantly enhanced growth rates in nitrogen yeast base media supplemented with various sugars; thus, these mutants were evaluated for their ability to serve as a starter for fermentation of Arabica coffee. The cupping scores of coffees derived from UV22-2 and UV22-3 were 83.5 ± 1.5 and 82.0 ± 2.14, respectively. The volatile compounds in the roasted coffee fermented by UV22-2 were analyzed by GC‒MS, which revealed higher levels of furfuryl alcohol and furfuryl acetate than did the other samples. These findings suggested that UV22-2 could be an influential starter culture for Arabica coffee fermentation.

Streptomyces sp. A3301, which produces lipase isolated by Panyachanakul et al. [1]. This optimization was done for the subsequent purification and characterization of the biological lipase produced by the isolate. The results showed that the strain produced lipase with a maximum activity of 321 U/mL using the optimal medium and conditions (1.5 % (w/v) xylose and 2 % (w/v) yeast extract, pH 7.0 at 30 °C, 150 rpm for 3 days). The specific activity of the purified lipase was 27,000 U/mg, which was 544 times the pre-purification level, based on hydrophobic chromatography. After ion-exchange chromatography, the specific activity was 5,600 U/mg, which was 113 times the pre-purification level, with a single-peak purification profile. The purified lipase had a single band based on SDS-PAGE analysis and the molecular mass was 45 kDa. The optimum temperature and thermo-stability of A3301 lipase were 60 and 30 - 55 °C, respectively. The optimum pH of the purified enzyme was pH 9.0, and the enzyme was stable in the pH range of 8.0 - 9.0. The purified lipase was stable in acetone, chloroform and toluene, with a high relative activity of 63 - 76 %. The immobilized strain was then applied to oily-wastewater treatment. The strain can remove oil and grease in synthetic wastewater containing oil at 1 - 3 % (v/v), with removal rates of 100, 99.82 and 99.68 %, respectively, after incubation for 6 days. It was then applied to oily-wastewater treatment from a restaurant, achieving the highest degradation rates of 98.53 % after treatment for 6 days. In addition, it also affected the Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) values decreasing. HIGHLIGHTS Optimization of lipase production by Streptomyces A3301. Purification and characterization of the lipase produced by the Streptomyces A3301. Application of the immobilized Streptomyces A3301 strain in the treatment of oily cooking wastewater. The immobilized Streptomyces A3301 strain has the capability to remove oil and grease in both synthetic mediums and restaurant wastewater. GRAPHICAL ABSTRACT

The thermo-solvent-tolerant lipase-producing actinomycete, Streptomyces sp. A3301, was utilized as a biocatalyst for poly (lactic acid) or PLA polymerization. The study aimed to optimize lipase immobilization conditions, characterize the immobilized lipase and apply it for PLA polymerization. The results showed using a sponge as the immobilizing matrix was the most effective method, achieving a maximum activity of 277 U/g of sponge. The optimal sponge size was determined to be 0.125 cm³ and pre-soaking the sponge in 0.1 M phosphate buffer at pH 7.0 for 24 h before use proved advantageous. Immobilization significantly enhanced the thermo-stability of the enzyme, with a relative activity ranging from 140 to 190 % within the temperature range of 30 to 60 °C. In contrast, the crude lipase exhibited thermo-stability only within the 30 - 50 °C range. The immobilized lipase demonstrated stability under PLA polymerization conditions, which involved a reaction mixture containing toluene and lactic acid and performed at 60 °C for 8 h. The immobilized lipase maintained its activity under this condition for 5 h, retaining a relative activity of 230 %, which was 1.2 times higher than the activity of the crude lipase. When the immobilized lipase was used in PLA polymerization, the resulting PLA product exhibited a molecular weight of 5,333 ± 0.02 Da, and the degree of polymerization was approximately 72. These findings underscore the potential of the immobilization technique to enhance lipase activity for PLA polymerization. HIGHLIGHTS PLA polymerization via a biological process is demonstrated. PLA can be polymerized by enzyme lipase produced by Streptomyces sp. A3301. Improving PLA polymerization with enzyme immobilization techniques. Sponge is the best immobilizer for PLA polymerization. PLA can be synthesized under mild conditions. GRAPHICAL ABSTRACT