Streptomyces albulus yields ε-poly-L-lysine and other products from salt-contaminated glycerol waste.

Actinomycetes are the most important microorganisms for the industrial production of secondary metabolites with antimicrobial and anticancer properties. However, they have not been implicated in biorefineries. Here, we study the ability of the ε-poly-L-lysine producing Streptomyces albulus BCRC 11814 to utilize biodiesel-derived crude glycerol. S. albulus was cultured in a mineral medium supplemented with up to 10% w/v sodium chloride or potassium chloride, and with crude glycerol as the sole carbohydrate source. Under these conditions, the strain produced 0.1 g ε-poly-L-lysine per 1 g of biomass. RNA sequencing revealed upregulation of the ectoine biosynthetic pathway of S. albulus, which provides proof of halotolerance. S. albulus has several silent secondary metabolite biosynthetic clusters predicted within the genome. Based on the results, we conclude that S. albulus BCRC 11814 is a halotolerant microorganism capable of utilizing biodiesel-derived crude glycerol better than other actinomycetes included in the present study. S. albulus has the potential to be established as microbial platform production host for a range of high-value biological products.

Biocatalytic conversion of aloeresin A to aloesin.

Leaf exudates from Aloe species, such as the Southern African Aloe ferox, are used in traditional medicines for both humans and livestock. This includes aloesin, a skin bleaching product that inhibits the synthesis of melanin. Aloesin, (a C-glycoside-5-methylchromone) can be released from aloeresin A, an ester of aloesin, through hydrolysis. The objective of the current study was to identify an enzymatic hydrolysis method for converting aloeresin A to aloesin, resulting in increased concentrations of aloesin in the aloe bitters extract. More than 70 commercially available hydrolytic enzymes were screened for the conversion of aloeresin A. An esterase (ESL001-02) from Diversa, a lipase (Novozym 388) and a protease (Aspergillus oryzae) preparation were identified during screening as being capable of providing conversion of pure aloeresin A, with the protease giving the best conversion (~100%). It was found that a contaminating enzyme in Novo 388 was responsible for the conversion of aloeresin A to aloesin. This contaminating enzyme, possibly a protease, was able to give almost complete conversion using crude aloe bitters extract, doubling the concentration of aloesin in aloe bitters extract via the hydrolysis of aloeresin A.