Effect of the purple non-sulfur bacterium (Rhodobacter sphaeroides) on the Brix, titratable acidity, ascorbic acid, organic acid, lycopene and β-carotene in tomato fruit

Author: Kensuke Kondo ^*, Noboru Nakata and Eiji Nishihara

Received 12 November 2009, accepted 2 April 2010.

Abstract

This study was conducted to investigate the effect of the purple non-sulfur bacterium (Rhodobacter sphaeroides) on the quality of tomato fruit (Lycopersicon esculentum Mill.). Freeze-dried dead purple non-sulfur bacterium (PTBP) was used for the investigation. The investigation also examined different PTBP application methods, by which PTBP was applied at one time or split-applied ten times. These PTBP application methods involved the application of three different amounts of PTBP; namely, 2.5 g PTBP (PTBP), 1.25 g PTBP (1/2 PTBP) and no PTBP (NO-PTBP). Nitrogen rates of 2.5 and 1.25 g (NH₄)₂SO₄ were applied for NO-PTBP and 1/2PTBP, respectively. Regardless of the method of application, PTBP promoted ascorbic acid content; however, there was no significant change in fruit weight or sugar, organic acid, lycopen and β-carotene contents. On the other hand, one-time application promoted malic acid content while ten-time application promoted phosphoric acid content. These results showed that PTBP application enhanced the quality of tomato fruit. Moreover, the effect of PTBP application differed with the method of application. Recently, consumer's demand for higher quality vegetables, from the shape to the nutritional value and healthiness is expanding. Therefore, PTBP application has the potential to improve the value of cultivated vegetables.

Key words: Phototrophic bacteria, Brix, titratable acidity, ascorbic acid, phosphoric acid, citric acid, malic acid, lycopene, β-carotene.