TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The step (b) is a continuous operation. The step (c) is a continuous operation. The step (d) further involves removing the solvent by heating the organic phase containing solvent and polyhydroxyalkanoate under atmospheric or vacuum distillation conditions. The step (e) further involves converting the biomass by heating under vacuum or atmospheric distillation conditions, where the remaining polyhydroxyalkanoate is converted to a biobased chemical product. The method further involves culturing a recombinant host with a renewable feedstock to produce a biomass. The method involves first heating at 40-170 degrees C, and second heating at 60-220 degrees C. The vacuum pressure is at least 700 mmHg or 0 mmHg. The method further involves recovering the gamma -butyrolactone product. The biobased product comprises less than 0.1 wt.% side products. The product is gamma -butyrolactone and is further processed to one or more of 1,4-butanediol (BDO), tetrahydrofuran (THF), N-methylpyrrolidone (NMP), N-ethyl pyrrolidone (NEP), 2-pyrrolidinone, N-vinylpyrrolidone (NVP) and polyvinylpyrrolidone (PVP). Preferred Components: The genetically engineered biomass is from a recombinant host having a poly-4-hydroxybutyrate pathway, where the host has an inhibiting mutation in its coenzyme A (CoA)-independent NAD-dependent succinic semialdehyde dehydrogenase gene or its CoA- independent NADP-dependent succinic semialdehyde dehydrogenase gene, or having the inhibiting mutations in both genes, and having stably incorporated one or more genes encoding one or more enzymes chosen from a succinyl-CoA transferase which is able to convert succinate to succinyl-CoA, succinate semialdehyde dehydrogenase which is able to convert succinyl-CoA to succinic semialdehyde, a succinic semialdehyde reductase which is able to convert succinic semialdehyde to 4-hydroxybutyrate, CoA transferase which is able to convert 4- hydroxybutyrate to 4-hydroxybutyryl-CoA, and a polyhydroxyalkanoate synthase which is able to polymerize 4- hydroxybutyryl-CoA to poly-4-hydroxybutyrate. The genetically engineered biomass is from a recombinant host having stably incorporated one or more genes encoding one or more enzymes chosen from a phosphoenolpyruvate carboxylase which is able to convert phosphoenolpyruvate to oxaloacetate, an isocitrate lyase which is able to convert isocitrate to glyoxalate, a malate synthase which is able to convert glyoxalate to malate and succinate, a succinate-CoA ligase (ADP-forming) which is able to convert succinate to succinyl-CoA, an NADP-dependent glyceraldeyde-3-phosphate dehydrogenase which is able to convert glyceraldehyde 3-phosphate to 1,3- bisphosphoglycerate forming NADPH+H+, an NAD-dependent glyceraldeyde-3-phosphate dehydrogenase which is able to convert glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate forming NADH+tT, a butyrate kinase which is able to convert 4-hydroxybutyrate to 4- hydroxybutyryl-phosphate, a phosphotransbutyrylase which is able to convert 4-hydroxybutyryl-phosphate to 4- hydroxybutyryl-CoA, and optionally having a disruption in one or more genes chosen from ynel, gabD, pyruvate kinase (pyk)F, pykA, macrophage erythroblast attacher (maeA) and maeB. The source of the renewable feedstock is chosen from glucose, fructose, sucrose, arabinose, maltose, lactose, xylose, methanol, ethanol, 1,4-butanediol, fatty acids, glycerin, vegetable oils, and biomass derived synthesis gas or its combination. The genetically engineered biomass is from a recombinant host having a poly-4-hydroxybutyrate pathway, and stably incorporated with one or more of genes encoding one or more above-mentioned enzymes. The biobased content of the gamma -butyrolactone product is at least 99%. The biobased content is 100%. The biobased chemical in the product is greater than 96%, or 95-99.5%, preferably 97-99.5%, more preferably 98-99.5% without any further processing of the product. The gamma -butyrolactone product comprises less than 0.05 wt.% side products. The crotonic acid product, delta -valerolactone product or acrylic acid product comprises less than 0.05 wt.% side products. The product yield is 76% or greater based on one gram of a gamma -butyrolactone in the product per gram of poly-4-hydroxybutyrate. The gamma -butyrolactone product comprises less than 0.1 wt.% side products, where the side products do not comprise acetamide, n-methyl pyrrolidone or n-ethyl pyrrolidone. The solvent is environmentally safe for human contact. The catalyst is sulfuric acid, phosphoric acid, hydrochloric acid, acetic acid, methane sulfonic acid, p-toluene sulphonic acid, trifluroacetic acid, zinc chloride, an ion exchange resin, potassium hydroxide, sodium hydroxide, calcium hydroxide or potassium carbonate. The catalyst is added at least 0.1-10 wt.% polyhydroxyalkanoate to the genetically engineered biomass. Preferred Microorganism: The biomass host is bacteria, yeast, fungi, algae, cyanobacteria, or its mixture of any two or more, preferably bacteria including Escherichia coli, Alcaligenes eutrophus (renamed as Ralstonia eutropha), Bacillus spp., A.latus, Azotobacter, Aeromonas, Comamonas, Pseudomonas, Ralstonia, Klebsiella, Synechococcus sp. PCC7002, PCC7942 and PCC6803, Chlorobium tepidum, Chloroflexus aurantiacus, Chromatium tepidum, C.vinosum, Rhodospirillum rubrum, Rhodobacter capsulatus, and Rhodopseudomonas palustris. The recombinant host is algae. Preferred Solvent: The solvent is 2-butanone, 2-pentanone, 3-pentanone, methyl isoamyl ketone, 2-heptanone, cyclohexanone, acetone, chloroform, methylene chloride, gamma - butyrolactone or gamma -hydroxybutyrate, preferably solvent is 2-pentanone containing up to 10 wt.% methyl isobutyl ketone. Preferred Composition: The pharmaceutical composition comprises a solid dosage tablet which releases 90 wt.%, preferably 99 wt.% sodium oxybate within one hour, preferably over a time period of 6-8 hours. The pharmaceutical composition further comprises an outer coating which releases 90 wt.% sodium oxybate in the outer coating in less than one hour. EXAMPLE - No suitable example given.