Biorefinery of chemicals from straw is an effective approach to alleviate the environmental pollution caused by straw burning. In this paper, we prepared gellan gum immobilized Lactobacillus bulgaricus T15 gel beads (LA-GAGR-T15 gel beads), characterized their properties, and established a continuous cell recycle fermentation process for D-lactate (D-LA) production using the LA-GAGR-T15 gel beads. The fracture stress of LA-GAGR-T15 gel beads was (91.68±0.11) kPa, which was 125.12% higher than that of the calcium alginate immobilized T15 gel beads (calcium alginate-T15 gel beads). This indicated that the strength of LA-GAGR-T15 gel beads was stronger, and the strain was less likely to leak out. The average D-LA production was (72.90±2.79) g/L after fermentation for ten recycles (720 h) using LA-GAGR-T15 gel beads as the starting strain and glucose as the substrate, which was 33.85% higher than that of calcium alginate-T15 gel beads and 37.70% higher than that of free T15. Subsequently, glucose was replaced by enzymatically hydrolyzed corn straw and fermented for ten recycles (240 h) using LA-GAGR-T15 gel beads. The yield of D-LA reached (1.74±0.79) g/(L·h), which was much higher than that of using free bacteria. The wear rate of gel beads was less than 5% after ten recycles, which indicated that LA-GAGR is a good carrier for cell immobilization and can be widely used in industrial fermentation. This study provides basic data for the industrial production of D-LA using cell-recycled fermentation, and provides a new way for the biorefinery of D-LA from corn straw.
Fermentation ; Lactobacillus delbrueckii ; Zea mays ; Lactic Acid ; Alginates/chemistry* ; Glucose

There is a limitation to estimate vitamin B12 intake due to the lack of data on vitamin B12 content of Korean commercial foods. In this study, vitamin B12 content was determined in favorite Korean restaurant foods, convenient or instant foods, fast foods and bakery products through a modified microbioassay using Lactobacillus delbrueckii ATCC 7830. Bulgogi and seafood & green pepper griddle had high vitamin B12 content, 3.50 and 2.96 microg/100 g, respectively. Pork suyook, pork griddle and pollack griddle had 0.48, 0.31 and 0.32 microg/100 g of vitamin B12, respectively. In stew, soft-tofu stew with seafood and doenjang stew with seafood had relatively high vitamin B12 content, 1.93 and 1.44 microg/100 g, respectively. Bibimbap and 4 different types of rice porridge, beef & mushroom, chicken & ginseng, seafood or abalone, had 0.36, 0.08, 0.09, 1.64 and 0.13 microg/100 g of vitamin B12, respectively. One serving of haejanggguk, yookejang, chuotang and galbitang had 5.97, 2.04, 2.63 and 1.91 microg of vitamin B12, respectively. One serving of samgetang and sulongtang had 2.89 microg and 6.64 microg of vitamin B12. In noodles, one serving of cram noodle soup, bibim-nangmyeon, and mul-nangmyeon had 18.8, 1.21 and 0.38 microg of vitamin B12, respectively. One regular gimbap and one triangle gimbap contained 1.09-2.53 and 0.54-1.11 microg of vitamin B12, respectively. One cheese-burger, chicken-burger and bulgogi-burger had 0.76, 0.62 and 0.54 microg of vitamin B12, respectively. A plain bagel and a waffle contained 0.13 and 0.17 microg/100 g of vitamin B12, respectively. Ready-made tomato sauce or cream sauce for spaghetti in a retort pouch contained only a trace of vitamin B12. In conclusion, these results should contribute to improving the present food vitamin B12 content database, most of which were cited from foreign data, thereby it could be helpful to estimate the vitamin B12 intake of Koreans more accurately than before. It will also provide new information for dietary education related to vitamin B12 and health.
Agaricales ; Capsicum ; Chickens ; Fast Foods ; Lactobacillus delbrueckii ; Lycopersicon esculentum ; Panax ; Restaurants ; Seafood ; Vitamin B 12 ; Vitamins