A genetically engineered strain of Pseudomonas is provided, which is capable of metabolizing lactose as a sole carbon source in the production of polyhydroxyalkanoates (PHAs). A method of engineering microorganisms and a method of PHA production are also provided, wherein lactose is used as a sole carbon source.

The present invention relates to a process of recovering an alkali metal sulfate, comprising: forming an organic acid fermentation liquid containing an alkali metal salt of organic acid; and adding sulfuric acid to the organic acid fermentation liquid to form and recover an alkali metal sulfate, wherein the alkali metal sulfate has a radioactivity concentration index of 1 or less, and to an alkali metal sulfate crystal comprising a predetermined peak in an X-ray diffraction spectrum (XRD) and having a radioactivity concentration index of 1 or less.