Production of lactic acid from byproducts of the food and vegetable processing industries without supplementation of the media

Lactic acid (LA) is the feedstock for the production of the biodegradable plastic polylactate that is used as a substitute for petroleum based plastics in some packaging applications. Currently, lactic acid for producing polylactate is obtained via fermentation of corn starch (after saccharification), and sugars from beets or sugarcane, practices that are usually questioned because they are in direct competition with their application as foods. One approach to remediate this concern is the use of byproducts from food and vegetable processing industries as feedstock for the production of lactic acid.;The objectives of this research were to search and characterize byproducts from the fruit and vegetable industries with fermentable sugars or starches that can be converted into fermentable sugars, and to test the feasibility of these byproducts to produce lactic acid via fermentation.;The byproducts from the fruits and vegetable processing industries used for this research were cucumbers, carrots, potatoes, watermelon, blueberries and blackberries that were obtained either from a local food processor or prepared in the laboratory. Byproducts were analyzed for total carbohydrates and fermentable sugars by phenol sulfuric acid and HPLC with pulsed amperometric detection (PAD). Total starch was determined using the Megazyme kit. Potato was hydrolyzed by heated 1.0 N HCl (90°C) at a ratio of 0.5:3 (w/v). Fermentation was conducted with Lactobacillus plantarum and Lactobacillus delbruekii for 80 hours under optimum conditions of temperature and pH.;Average amount of total carbohydrates contained in the byproducts ranged from 2.3 % for cucumbers to 12.4% for blueberries. Total fermentable sugars were in the range of 0.009 to 8.2% for glucose and 0.003 to 9.3% for fructose. Intermediate values were obtained for total carbohydrate and fermentable sugars for the other byproducts. Potato wastes had 63.9 % starch on a dry basis which was converted into fermentable sugars after acid hydrolysis.;The amount of LA produced at the end of fermentations was dependent on the microorganism and the byproduct. Lactobacillus plantarum produced LA in the range of 0.42 to 1.90 g/100g of byprouduct for hydrolyzed potato and cucumber at the end of fermentation and 0.92 to 3.80 g/100g of byproduct in as is basis after pH modification to 2.8 for black berry prescake and cucumber, respectively. Lactobacillus delbruekii generated LA in the range 0.94 to 1.74 g/100g of byproduct at the end of fermenation for hydrolzyed potato and cucumber at the end of fermentation and 1.90 to 3.50 g/100g of byproduct for black berry presscake and seeedless watermelon after pH modifictation to 2.8 respectively with intermediate values for all the other byproducts.;This research demonstrated that byproducts from the fruit and vegetable industries used in this study can be used in the production of LA through microbial fermentation. Some of the byproducts can serve as an alternative to traditional feedstocks.